Reception apparatus

ABSTRACT

A reception apparatus includes a plurality of antennas for receiving modulation signals of channels in the same frequency band, an received signal strength intensity estimation unit for estimating the reception received signal strength intensity of each reception signal, transmission path fluctuation estimation units for estimating a transmission path fluctuation of each channel of the reception signal, phase difference estimation units for calculating a phase difference of the transmission path fluctuation estimation signal of a predetermined channel of each antenna and outputting it as a phase difference signal, and a signal selection unit for selecting and outputting a reception quadrate baseband signal for isolating a signal of each channel from the reception signals and a transmission path fluctuation estimation signal of each channel. Thus, by isolating and demodulating a plurality of muliplexed modulated signals received, it is possible to improve the data transmission rate.

TECHNICAL FIELD

[0001] The present invention relates to a transmission method formultiplexing modulation signals of a plurality of channels to the samefrequency band, a transmission apparatus and a reception apparatus.

BACKGROUND ART

[0002] This kind of transmission method and reception method have beenavailable such as the ones disclosed in Japanese Patent ApplicationNon-Examined Publication No. 2002-44051. FIG. 87 illustrates thetransmission method and the reception method disclosed in the foregoingpublication.

[0003] In FIG. 87, first space-time encoder STE1 (8705) receives firstdata block b1 [n, k], and second space-time encoder STE2 (8707) receivessecond data block b2 [n, k], and two signals coded by encoders STE1 andSTE 2 respectively are modulated by inverse fast Fourier transformersIFFT (8708-8711). Then the modulated signals are transmitted as OFDM(orthogonal frequency division multiplexing) signals by fourtransmitting antennas TA1 (8712)-TA4 (8715).

[0004] A plurality of receiving antennas RA1 (8701)-RAP (8703) receivethose signals transmitted by antennas TA1 (8712)-TA4 (8715). Receptionsignals r1 [n, k] (8716)-rp (8718) are transformed by fast Fouriertransformation (FET) sub-systems FFT1 (8719)-FFTP (8721) respectively,and supplied to space-time processor STP (8722). Processor STP (8722)detects signal information and supplies it to first and secondspace-time decoders STD1 (8723) and STD2 (8724). Channel parameterestimation unit CPE (8725) receives the transformed signal, anddetermines channel-parameter information, then supplies the informationto the space-time processor STP (8722) for demodulating the signals.

[0005] However, the foregoing conventional structure gives no thought tothe synchronization between channels in the same frequency band as wellas a frequency offset. As a result, this structure encounters thedifficulty of achieving the most important factor in order to demultiplea multiplexed signal, namely, obtaining an accuracy of estimatingchannels.

DISCLOSURE OF THE INVENTION

[0006] The present invention aims to provide a reception apparatus thatcan estimate channels accurately and with ease from multiplexedmodulation signals.

[0007] The reception apparatus of the present invention comprises thefollowing elements:

[0008] a plurality of antennas for receiving modulation signals of aplurality of channels available in an idential frequency band;

[0009] a field electric intensity estimation unit for estimating areception field electric intensity of reception signals received by theplurality of antennas, and outputting a reception received signalstrength intensity estimation signal of the respective receptionsignals;

[0010] a transmission path fluctuation estimation unit for estimating atransmission path fluctuation of respective channels of the respectivereception signals, and outputting a transmission path fluctuationestimation signal;

[0011] a phase difference estimation unit for receiving the transmissionpath fluctuation estimation signals of given channels supplied from therespective antennas, and finding a phase difference between thetransmission path fluctuation estimation signals of the given channels,then outputting a phase difference signal; and

[0012] a signal selector for receiving a reception quadrate basebandsignal supplied from the respective antennas, the transmission pathfluctuation estimation signals of given channels supplied from therespective antennas, reception received signal strength intensityestimation signals of the respective reception signals, and the phasedifference signal, then selecting the reception quadrate baseband signaland the transmission path fluctuation estimation signals of givenchannels for isolating signals of the respective channels from thereception signals before outputting the signals selected.

[0013] The foregoing structure multiplexes the modulation signals of aplurality of channels to the same frequency, thereby increasing the datatransmission rate. At the same time, an antenna for demodulation isselected by using the phase difference and the received signal strengthintensity as parameters, so that the antenna in the best condition canbe selected. As a result, the data transmission quality can be improved.

[0014] A reception apparatus of the present invention comprises thefollowing elements:

[0015] a plurality of antennas for receiving modulation signals of aplurality of spread-spectrum communication methods transmitted to thesame frequency band;

[0016] a field electric intensity estimation unit for estimating areception field electric intensity of reception signals received by theplurality of antennas, and outputting a reception received signalstrength intensity estimation signal of the respective receptionsignals;

[0017] a transmission path fluctuation estimation unit for estimating atransmission path fluctuation of respective spread-spectrumcommunication methods of the respective reception signals, andoutputting a transmission path fluctuation estimation signal;

[0018] a phase difference estimation unit for receiving the transmissionpath fluctuation estimation signals, and finding a phase differencebetween the transmission path fluctuation estimation signals of thegiven channels, then outputting a phase difference signal; and

[0019] a signal selector for receiving a reception quadrate basebandsignal supplied from the respective antennas, the transmission pathfluctuation estimation signals, reception received signal strengthintensity estimation signals of the respective reception signals, andthe phase difference signal, then selecting the reception quadratebaseband signal and the transmission path fluctuation estimation signalsfor isolating signals of the respective spread-spectrum communicationmethods from the reception signals before outputting the signalsselected.

[0020] The foregoing structure multiplexes the modulation signals of aplurality of channels to the same frequency, thereby increasing the datatransmission rate. At the same time, an antenna for demodulation isselected using the phase difference and the received signal strengthintensity as parameters, so that the antenna in the best condition canbe selected. As a result, the data transmission quality can be improved,and a propagation path can be estimated with ease.

[0021] A reception apparatus of the present invention comprises thefollowing elements:

[0022] a plurality of antennas for receiving modulation signalstransmitted by a transmission method by which:

[0023] a transmission apparatus transmits modulation signals of aplurality of channels available in the same frequency band from aplurality of antennas, and a symbol for time-synchronization is includedin a signal transmitted from only a given antenna, and while this symbolis transmitted, in the signals transmitted from other antennas, the samephase and quadrate signals in the in-phase-quadrature plane are made tobe zero signals,

[0024] a synchronizing unit, prepared for each one of the antennas, forsynchronizing with the transmission apparatus time-wise using areception signal; and

[0025] a radio-wave propagation environment estimation unit, preparedfor each one of the antennas, for estimating a radio-wave propagationenvironment from the reception signals.

[0026] A signal supplied from a synchronizing unit corresponding to theantenna, which is estimated having the best radio-wave propagationenvironment, is used as a time-synchronization signal for synchronizingwith the transmission apparatus.

[0027] The foregoing structure multiplexes the modulation signals of aplurality of channels to the same frequency, thereby increasing the datatransmission rate. At the same time, the reception apparatus receivesthe symbol, which is used for estimating time-synchronization,transmitted through one channel from the transmission apparatus, therebyobtaining the time-synchronization common to the plurality of channels.The most reliable signal is selected out of time-synchronization signalssupplied from the respective antennas, so that an estimation accuracycan be increased.

[0028] A reception apparatus of the present invention comprises thefollowing elements:

[0029] a plurality of antennas for receiving modulation signalstransmitted by a transmission method by which:

[0030] a transmission apparatus transmits modulation signals of aplurality of channels available in the same frequency band from aplurality of antennas, and a symbol for estimating a frequency offset isincluded in a signal transmitted from only a given antenna, and whilethis symbol is transmitted, in the signals transmitted from otherantennas, both of the same phase signal and a quadrate signal in thein-phase-quadrature plane are made to be zero signals;

[0031] a frequency-offset estimation unit, prepared for each one of theantennas, for estimating a frequency offset between the receptionapparatus and the transmission apparatus with the reception signal; and

[0032] a radio-wave propagation environment estimation unit, preparedfor each one of the antennas, for estimating a radio-wave propagationenvironment.

[0033] A signal supplied from a frequency offset estimation unitcorresponding to the antenna, which antenna is estimated having the bestradio-wave propagation environment, is used for removing the frequencyoffset.

[0034] The foregoing structure multiplexes the modulation signals of aplurality of channels to the same frequency, thereby increasing the datatransmission rate. At the same time, the reception apparatus receivesthe symbol, which is used for estimating a frequency offset, transmittedthrough one channel from the transmission apparatus, so that thefrequency offset common to the signals of the plurality of channels canbe estimated. The frequency offset estimation unit is prepared to eachone of the antennas, and the signal supplied from the antenna, which hasthe best reception received signal strength intensity, is used forremoving the frequency offset. As a result, the frequency offset can beaccurately removed.

[0035] As discussed above, in a communication method which multiplexesmodulation signals of a plurality of channels to the same frequencyband, a reception apparatus selects an antenna, which has the bestenvironment, by estimating a radio-wave propagation environment, such asa received signal strength intensity, from a reception signal. Thereception apparatus then uses symbols, included in the signals suppliedfrom the selected antenna, for estimating a phase difference,time-synchronization, or removing a frequency offset. Throughmultiplexing the modulation signals of a plurality of channels to thesame frequency band, the foregoing operation and structureadvantageously allow increasing the data transmission rate, and alsoallow the reception apparatus to demultiplex the multiplexed modulationsignals with ease.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 shows frame structures of channel A and channel B inaccordance with a first exemplary embodiment of the present invention.

[0037]FIG. 2 shows a structure of a transmission apparatus in accordancewith the first exemplary embodiment of the present invention.

[0038]FIG. 3 shows a structure of a modulation signal generator inaccordance with the first exemplary embodiment of the present invention.

[0039]FIG. 4 shows a point mapping of signals in in-phase-quadratureplane in accordance with the first exemplary embodiment of the presentinvention.

[0040]FIG. 5 shows a structure of a reception apparatus in accordancewith the first exemplary embodiment of the present invention.

[0041]FIG. 6 shows relations between symbols, transmission pathvariations and reception quadrature baseband signals in accordance withthe first exemplary embodiment of the present invention.

[0042]FIG. 7 shows frame structures of channel A and channel B inaccordance with the first exemplary embodiment of the present invention.

[0043]FIG. 8 shows a structure of a reception apparatus in accordancewith a second exemplary embodiment of the present invention.

[0044]FIG. 9 shows a structure of a reception apparatus in accordancewith the second exemplary embodiment of the present invention.

[0045]FIG. 10 shows a transmission path variation estimation signal inaccordance with the second exemplary embodiment of the presentinvention.

[0046]FIG. 11 shows frame structures of signals in accordance with athird exemplary embodiment of the present invention.

[0047]FIG. 12 shows a structure of a transmission apparatus inaccordance with the third exemplary embodiment of the present invention.

[0048]FIG. 13 shows a structure of a modulation signal generator inaccordance with the third exemplary embodiment of the present invention.

[0049]FIG. 14 shows relations between pilot symbols and codes tomultiply in accordance with the third exemplary embodiment of thepresent invention.

[0050]FIG. 15 shows a structure of a reception apparatus in accordancewith the third exemplary embodiment of the present invention.

[0051]FIG. 16 shows a structure of a transmission path variationestimation unit in accordance with the third exemplary embodiment of thepresent invention.

[0052]FIG. 17 shows amounts of fluctuation in a transmission path alongthe timing axis in accordance with the third exemplary embodiment of thepresent invention.

[0053]FIG. 18 shows a structure of a reception apparatus in accordancewith a fourth exemplary embodiment of the present invention.

[0054]FIG. 19 shows a structure of a reception apparatus in accordancewith the fourth exemplary embodiment of the present invention.

[0055]FIG. 20 shows a frame structure of a signal in accordance with afifth exemplary embodiment of the present invention.

[0056]FIG. 21 shows a point mapping of signals in in-phase-quadrature(I-Q) plane in accordance with the fifth exemplary embodiment of thepresent invention.

[0057]FIG. 22 shows a structure of a modulation signal generator inaccordance with the fifth exemplary embodiment of the present invention.

[0058]FIG. 23 shows a structure of a transmission path variationestimation unit in accordance with the fifth exemplary embodiment of thepresent invention.

[0059]FIG. 24 shows frame structures of channel A and channel B inaccordance with the fifth exemplary embodiment of the present invention.

[0060]FIG. 25 shows a structure of a transmission apparatus inaccordance with a sixth exemplary embodiment of the present invention.

[0061]FIG. 26 shows a structure of a reception apparatus in accordancewith the sixth exemplary embodiment of the present invention.

[0062]FIG. 27 shows distortions in transmission paths in accordance withthe sixth exemplary embodiment of the present invention.

[0063]FIG. 28 shows structures of structures of a transmission pathvariation estimation unit and a signal processor in accordance with thesixth exemplary embodiment of the present invention.

[0064]FIG. 29 shows frame structures of signals in accordance with aseventh exemplary embodiment of the present invention.

[0065]FIG. 30 shows frame structures of signals in accordance with theseventh exemplary embodiment of the present invention.

[0066]FIG. 31 shows a transmission apparatus at a base station inaccordance with the seventh exemplary embodiment of the presentinvention.

[0067]FIG. 32 shows a structure of a reception apparatus at a terminalin accordance with the seventh exemplary embodiment of the presentinvention.

[0068]FIG. 33 shows a frame structure along a time axis in accordancewith an eighth exemplary embodiment of the present invention.

[0069]FIG. 34 shows a frame structure along a time axis in accordancewith the eighth exemplary embodiment of the present invention.

[0070]FIG. 35 shows a structure of a modulation signal generator inaccordance with the eighth exemplary embodiment of the presentinvention.

[0071]FIG. 36 shows a structure of a modulation signal generator inaccordance with the eighth exemplary embodiment of the presentinvention.

[0072]FIG. 37 shows a structure of a reception apparatus in accordancewith the eighth exemplary embodiment of the present invention.

[0073]FIG. 38 shows a structure of a reception apparatus in accordancewith the eighth exemplary embodiment of the present invention.

[0074]FIG. 39 shows a structure of a reception apparatus in accordancewith the eighth exemplary embodiment of the present invention.

[0075]FIG. 40 shows a structure of a reception apparatus in accordancewith the eighth exemplary embodiment of the present invention.

[0076]FIG. 41 shows a structure of a reception apparatus in accordancewith the eighth exemplary embodiment of the present invention.

[0077]FIG. 42 shows a structure of a reception apparatus in accordancewith the eighth exemplary embodiment of the present invention.

[0078]FIG. 43 shows a frame structure along a time axis in accordancewith a ninth exemplary embodiment of the present invention.

[0079]FIG. 44 shows a frame structure along a time axis in accordancewith the ninth exemplary embodiment of the present invention.

[0080]FIG. 45 shows a frame structure along a time axis in accordancewith the ninth exemplary embodiment of the present invention.

[0081]FIG. 46 shows a structure of a modulation signal generator inaccordance with the ninth exemplary embodiment of the present invention.

[0082]FIG. 47 shows a structure of a modulation signal generator inaccordance with the ninth exemplary embodiment of the present invention.

[0083]FIG. 48 shows a structure of a modulation signal generator inaccordance with the ninth exemplary embodiment of the present invention.

[0084]FIG. 49 shows a structure of a modulation signal generator inaccordance with the ninth exemplary embodiment of the present invention.

[0085]FIG. 50 shows a frame structure along a time axis and a frequencyaxis in accordance with a tenth exemplary embodiment of the presentinvention.

[0086]FIG. 51 shows a frame structure along a time axis and a frequencyaxis in accordance with the tenth exemplary embodiment of the presentinvention.

[0087]FIG. 52 shows a structure of a reception apparatus in accordancewith the tenth exemplary embodiment of the present invention.

[0088]FIG. 53 shows a structure of a reception apparatus in accordancewith the tenth exemplary embodiment of the present invention.

[0089]FIG. 54 shows a structure of a reception apparatus in accordancewith the tenth exemplary embodiment of the present invention.

[0090]FIG. 55 shows a structure of a reception apparatus in accordancewith the tenth exemplary embodiment of the present invention.

[0091]FIG. 56 shows a structure of a reception apparatus in accordancewith the tenth exemplary embodiment of the present invention.

[0092]FIG. 57 shows a structure of a reception apparatus in accordancewith the tenth exemplary embodiment of the present invention.

[0093]FIG. 58 shows a structure of a reception apparatus in accordancewith an eleventh exemplary embodiment of the present invention.

[0094]FIG. 59 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0095]FIG. 60 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0096]FIG. 61 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0097]FIG. 62 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0098]FIG. 63 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0099]FIG. 64 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0100]FIG. 65 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0101]FIG. 66 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0102]FIG. 67 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0103]FIG. 68 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0104]FIG. 69 shows a structure of a reception apparatus in accordancewith the eleventh exemplary embodiment of the present invention.

[0105]FIG. 70 shows a frame structure in accordance with a twelfthexemplary embodiment of the present invention.

[0106]FIG. 71 shows a structure of a information symbol in accordancewith the twelfth exemplary embodiment of the present invention.

[0107]FIG. 72 shows a structure of a information symbol in accordancewith the twelfth exemplary embodiment of the present invention.

[0108]FIG. 73 shows a structure of a information symbol in accordancewith the twelfth exemplary embodiment of the present invention.

[0109]FIG. 74 shows a structure of a transmission apparatus inaccordance with the twelfth exemplary embodiment of the presentinvention.

[0110]FIG. 75 shows a structure of a reception apparatus in accordancewith the twelfth exemplary embodiment of the present invention.

[0111]FIG. 76 shows a structure of a transmission apparatus inaccordance with the twelfth exemplary embodiment of the presentinvention.

[0112]FIG. 77 shows a structure of a reception apparatus in accordancewith the twelfth exemplary embodiment of the present invention.

[0113]FIG. 78 shows a structure of a transmission apparatus inaccordance with the twelfth exemplary embodiment of the presentinvention.

[0114]FIG. 79 shows a frame structure in accordance with a thirteenthexemplary embodiment of the present invention.

[0115]FIG. 80 shows a structure of a transmission apparatus inaccordance with the thirteenth exemplary embodiment of the presentinvention.

[0116]FIG. 81 shows a structure of a control symbol in accordance withthe thirteenth exemplary embodiment of the present invention.

[0117]FIG. 82 shows a structure of a reception apparatus in accordancewith the thirteenth exemplary embodiment of the present invention.

[0118]FIG. 83 shows a frame structure in accordance with the thirteenthexemplary embodiment of the present invention.

[0119]FIG. 84A shows a frame structure of a transmission signal from abase station in accordance with the twelfth exemplary embodiment of thepresent invention.

[0120]FIG. 84B shows a frame structure of the transmission signal from aterminal in accordance with the twelfth exemplary embodiment of thepresent invention.

[0121]FIG. 85 shows a structure of a control symbol in accordance withthe thirteenth exemplary embodiment of the present invention.

[0122]FIG. 86 shows a structure of a control symbol in accordance withthe thirteenth exemplary embodiment of the present invention.

[0123]FIG. 87 shows a block diagram illustrating parts of a conventionalMIMO-OFDM system.

BEST MODE FOR PRACTICING THE INVENTION

[0124] Exemplary embodiments of the present invention are demonstratedhereinafter with reference to the accompanying drawings. In thefollowing descriptions, “antenna” does not always mean a single antenna,but “antenna” means an antenna unit which is formed of a plurality ofantennas.

[0125] Exemplary Embodiment 1

[0126] In a transmission method where modulation signals of a pluralityof channels are multiplexed to the same frequency band, at the time whena demodulation symbol is inserted in a channel, in another channelsymbol, the same phase and quadrature signals in the in-phase-quadratureplane are made to be zero signals. The foregoing method and atransmission apparatus as well as a reception apparatus employed in themethod are described in this first embodiment.

[0127]FIG. 1 shows frame structure 120 of channel A and frame structure130 of channel B along a time axis. Channel A has pilot symbols 101,104, 107, guard symbols 102, 105, 108, and data symbol 103, 106. Datasymbols, for instance, have undergone QPSK (quadrature phase shiftkeying) modulation. Channel B has guard symbols 109, 112, 115, pilotsymbols 110, 113, 116, and data symbols 111, 114. Data symbols, forinstance, have undergone QPSK modulation.

[0128] Pilot symbol 101 of channel A and guard symbol 109 of channel Bare placed at an identical time, and the following combinations areplaced at an identical time respectively:

[0129] guard symbol 102 of channel A and pilot symbol 110 of channel B;

[0130] data symbol 103 of channel A and data symbol 111 of channel B;

[0131] pilot symbol 104 of channel A and guard symbol 112 of channel B;

[0132] guard symbol 105 of channel A and pilot symbol 113 of channel B;

[0133] data symbol 106 of channel A and data symbol 114 of channel B;

[0134] pilot symbol 107 of channel A and guard symbol 115 of channel B;

[0135] guard symbol 108 of channel A and pilot symbol 116 of channel B.

[0136]FIG. 2 shows a structure of a transmission apparatus of this firstembodiment, and the apparatus is formed of channel A transmitter 220,channel B transmitter 230, and frame signal generator 209. Channel Atransmitter 220 is formed of modulation signal generator 202, radio unit204, power amplifier 206, and antenna 208. Channel B transmitter 230 isformed of modulation signal generator 212, radio unit 214, poweramplifier 216, and antenna 218.

[0137] Modulation signal generator 202 of channel A receives framesignal 210 and transmission digital signal 201 of channel A, and outputsmodulation signal 203 in accordance with the frame structure.

[0138] Radio unit 204 of channel A receives modulation signal 203 ofchannel A, and outputs transmission signal 205 of channel A.

[0139] Power amplifier 206 of channel A receives transmission signal 205of channel A, amplifies signal 205, and outputs transmission signal 207of channel A as radio wave from antenna 208 of channel A.

[0140] Frame generator 209 outputs frame signal 210.

[0141] Modulation signal generator 212 of channel B receives framesignal 210 and transmission digital signal 211 of channel B, and outputsmodulation signal 213 in accordance with the frame structure.

[0142] Radio unit 214 of channel B receives modulation signal 213 ofchannel B, and outputs transmission signal 215 of channel B.

[0143] Power amplifier 216 of channel B receives transmission signal 215of channel B, amplifies signal 215, and outputs transmission signal 217of channel B as radio wave from antenna 218 of channel B.

[0144]FIG. 3 shows a detailed structure of modulation signal generators202, 212 shown in FIG. 2. Data symbol modulation signal generator 302receives transmission digital signal 301 and frame signal 311. Whenframe signal 311 indicates a data symbol, generator 302 provides signals301 with QPSK modulation, and outputs in-phase component 303 andquadrature-phase component 304 of a transmission quadrature basebandsignal of the data symbol.

[0145] Pilot symbol modulation signal generator 305 receives framesignal 311. When signal 311 indicates a pilot symbol, generator 305outputs in-phase component 306 and quadrature-phase component 307 of atransmission quadrature baseband signal of the pilot symbol.

[0146] Guard symbol modulation generator 308 receives frame signal 311.When signal 311 indicates a guard symbol, generator 308 outputs in-phasecomponent 309 and quadrature-phase component 310 of a transmissionquadrature baseband signal of the guard symbol.

[0147] In-phase component switcher 312 receives in-phase components 303,306, 309 and frame signal 311, then selects the in-phase component oftransmission quadrature baseband signal corresponding to a symbolindicated by frame signal 311, and outputs the selected one as in-phasecomponent 313 of the selected transmission quadrature baseband signal.

[0148] Quadrature-phase component switcher 314 receives quadrature-phasecomponents 304, 307, 310, and frame signal 311, then selects aquadrature-phase component of a transmission quadrature baseband signalcorresponding to a symbol indicated by frame signal 311, and outputs theselected one as quadrature-phase component 315 of the selectedtransmission quadrature baseband signal.

[0149] Orthogonal modulator 316 receives in-phase component 313selected, quadrature-phase component 315 selected, then provides thosecomponents 313, 315 with orthogonal modulation, and outputs modulationsignal 317.

[0150]FIG. 4 shows point-placement of signals of QPSK (data symbol),pilot symbol, guard symbol, such as QPSK signal-point 401, pilot symbolsignal-point 402, and guard symbol signal-point 403.

[0151]FIG. 5 shows a structure of a reception apparatus in accordancewith the first embodiment. Radio unit 503 receives signal 502 receivedby antenna 501, and outputs in-phase component 504 and quadrature-phasecomponent 505 of reception quadrature baseband signal.

[0152] Transmission path variation estimation unit 506 of channel Areceives reception quadrature baseband signals 504, 505, then estimatesa transmission path variation of channel A, and outputs transmissionpath variation estimation signal 507 of channel A.

[0153] Transmission path variation estimation unit 508 of channel Breceives reception quadrature baseband signals 504, 505, then estimatesa transmission path variation of channel B, and outputs transmissionpath variation estimation signal 509 of channel B.

[0154] Delay unit 510 receives in-phase component 504 andquadrature-phase component 505 of the reception quadrature basebandsignal, and outputs in-phase component 511 and quadrature-phasecomponent 512 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 507 and 509 of channel A and channel B.

[0155] Radio unit 515 receives signal 514 received by antenna 513, andoutputs in-phase component 516 and quadrature-phase component 517 of thereception quadrature baseband signal.

[0156] Transmission path variation estimation unit 518 of channel Areceives reception quadrature baseband signals 516 and 517, thenestimates a transmission path variation of channel A, and outputstransmission path variation estimation signal 519 of channel A.

[0157] Transmission path variation estimation unit 520 of channel Breceives reception quadrature baseband signals 516 and 517, thenestimates a transmission path variation of channel B, and outputstransmission path variation estimation signal 521 of channel B.

[0158] Delay unit 522 receives in-phase component 516 andquadrature-phase component 517 of the reception quadrature basebandsignal, and outputs in-phase component 523 and quadrature-phasecomponent 524 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 519 and 521 of channel A and channel B.

[0159] Signal processor 525 receives the following signals:

[0160] transmission path variation estimation signal 507 of channel A;

[0161] transmission path variation estimation signal 509 of channel B;

[0162] in-phase component 511 and quadrature-phase component 512 ofdelayed reception quadrature baseband signal;

[0163] transmission path variation estimation signal 519 of channel A;

[0164] transmission path variation estimation signal 521 of channel B;and

[0165] in-phase component 523 and quadrature-phase component 524 ofdelayed reception quadrature baseband signal.

[0166] Then signal processor 525 outputs the following signals:

[0167] in-phase component 526 and quadrature-phase component 527 ofreception quadrature baseband signal of channel A; and

[0168] in-phase component 530 and quadrature-phase component 531 ofreception quadrature baseband signal of channel B.

[0169] Demodulator 528 receives in-phase component 526 andquadrature-phase component 527 of reception quadrature baseband signalof channel A, then demodulates those components, and outputs receptiondigital signal 529 of channel A.

[0170] Demodulator 532 receives in-phase component 530 andquadrature-phase component 531 of reception quadrature baseband signalof channel B, then demodulates those components, and outputs receptiondigital signal 533 of channel B.

[0171]FIG. 6 shows relation between a frame structure 620 of channel Aand a frame structure 630 of channel B, symbols 601-616 of each channelat certain times, transmission path variations 621 and 631 of channels Aand B, and reception quadrature baseband signal 632. Channel A has thefollowing symbols: pilot symbols 601, 607; guard symbols 602, 608; datasymbols 603, 604, 605, and 606. Channel B has the following symbols:guard symbols 609, 615; pilot symbols 610, 616; data symbols 611, 612,613, and 614.

[0172] Pilot symbol 601 of channel A and guard symbol 609 of channel Boccur at time 0, and the following combinations occur at time 1, time 2,time 3, time 4, time 5, time 6, and time 7 respectively:

[0173] guard symbol 602 of channel A and pilot symbol 610 of channel B;

[0174] data symbol 603 of channel A and data symbol 611 of channel B;

[0175] data symbol 604 of channel A and data symbol 612 of channel B;

[0176] data symbol 605 of channel A and data symbol 613 of channel B;

[0177] data symbol 606 of channel A and data symbol 614 of channel B;

[0178] pilot symbol 607 of channel A and guard symbol 615 of channel B;

[0179] guard symbol 608 of channel A and pilot symbol 616 of channel B.

[0180]FIG. 7 shows a structure of channel A frame 720 and a structure ofchannel B frame 730 along a time axis. Channel A has the followingsymbols: pilot symbols 701, 702, 706, 707; guard symbols 703, 704, 708,709; and data symbol 705. Channel B has the following symbols: guardsymbols 710, 711, 715, 716; pilot symbols 712, 713, 717, 718; and datasymbol 714. Data symbol 705 of channel A and data symbol 714 of channelB have undergone QPSK modulation.

[0181] Pilot symbol 701 of channel A and guard symbol 710 of channel Boccur at an identical time, and the following combinations occur at anidentical time respectively:

[0182] pilot symbol 702 of channel A and guard symbol 711 of channel B;

[0183] guard symbol 703 of channel A and pilot symbol 712 of channel B;

[0184] guard symbol 704 of channel A and pilot symbol 713 of channel B;

[0185] data symbol 705 of channel A and data symbol 714 of channel B;

[0186] pilot symbol 706 of channel A and guard symbol 715 of channel B;

[0187] pilot symbol 707 of channel A and guard symbol 716 of channel B;

[0188] guard symbol 708 of channel A and pilot symbol 717 of channel B;

[0189] guard symbol 709 of channel A and pilot symbol 718 of channel B.

[0190] An operation of the transmission apparatus is demonstratedherein-after with reference to FIG. 1 through FIG. 4. In FIG. 2, framesignal generator 209 outputs the information of the frame structureshown in FIG. 1 as frame signal 210. Modulation signal generator 202 ofchannel A receives frame signal 210 and transmission digital signal 201of channel A, then outputs modulation signal 203 of channel A inaccordance with the frame structure. Modulation signal generator 212 ofchannel B receives frame signal 210 and transmission digital signal 211of channel B, then outputs modulation signal 213 of channel B inaccordance with the frame structure.

[0191] An operation of modulation signal generators 202 and 212 in theprocess discussed above is described using transmitter 220 of channel Aas an example with reference to FIG. 3.

[0192] Data symbol modulation signal generator 302 receives transmissiondigital signal 301, i.e. transmission digital signal 201 of channel A inFIG. 2, and frame signal 311, i.e. frame signal 210 in FIG. 2. Whenframe signal 311 indicates a data symbol, generator 302 provides signal201 with QPSK modulation, and outputs in-phase component 303 andquadrature-phase component 304 of a transmission quadrature basebandsignal of the data symbol.

[0193] Pilot symbol modulation signal generator 305 receives framesignal 311. When signal 311 indicates a pilot symbol, generator 305outputs in-phase component 306 and quadrature-phase component 307 of atransmission quadrature baseband signal of the pilot symbol.

[0194] Guard symbol modulation signal generator 308 receives framesignal 311. When signal 311 indicates a guard symbol, generator 308outputs in-phase component 309 and quadrature-phase component 310 of atransmission quadrature baseband signal of the guard symbol.

[0195]FIG. 4 shows signal-point placement of the respective symbols inan in-phase-quadrature plane of the foregoing operation. Points 401 inFIG. 4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 402 indicate the signal-points ofin-phase component 306 and quadrature-phase component 307 of thetransmission quadrature baseband signal of the pilot symbol. Point 403indicates the signal-points of in-phase component 309 andquadrature-phase component 310 of the transmission quadrature basebandsignal of the guard symbol.

[0196] In-phase component switcher 312 receives the following signals:

[0197] in-phase component 303 of data symbol transmission quadraturebaseband signal;

[0198] in-phase component 306 of pilot symbol transmission quadraturebaseband signal;

[0199] in-phase component 309 of guard symbol transmission quadraturebaseband signal; and

[0200] frame signal 311.

[0201] Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe signal 311, and outputs the selected one as in-phase component 313of the selected transmission quadrature baseband signal.

[0202] Quadrature-phase component switcher 314 receives the followingsignals:

[0203] quadrature-phase component 304 of data symbol transmissionquadrature baseband signal;

[0204] quadrature-phase component 307 of pilot symbol transmissionquadrature baseband signal;

[0205] quadrature-phase component 310 of guard symbol transmissionquadrature baseband signal; and

[0206] frame signal 311.

[0207] Switcher 314 then selects aquadrature-phase component of atransmission quadrature baseband signal corresponding to the symbolindicated by frame signal 311, and outputs the selected one asquadrature-phase component 315 of the selected transmission quadraturebaseband signal.

[0208] Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal317, i.e. signal 203 shown in FIG. 2.

[0209] An operation of the reception apparatus, in particular, oftransmission path variation estimation unit 506 of channel A,transmission path variation estimation unit 508 of channel B, and signalprocessor 525, with reference to FIG. 5 and FIG. 6.

[0210] In-phase component 504 and quadrature-phase component 505 ofreception quadrature baseband signal of the signal received by antenna501 shown in FIG. 5 are taken as examples for description with referenceto FIG. 6.

[0211] In FIG. 6, at time 0 (zero), pilot symbol 601 of channel A andguard symbol 609 of channel B are multiplexed together. Assume thatin-phase component 504 and quadrature-phase component 505 of thereception quadrature baseband signal are I0 and Q0 respectively, and thetransmission path variation of channel A and that of channel B are (Ia0,Qa0) and (Ib0, Qb0) respectively. Since the transmission apparatustransmits 0 (zero) at the guard symbol of channel B, in-phase component504 and quadrature-phase component 505 of the reception quadraturebaseband signal, namely, I0 and Q0, are formed of the component of pilotsymbol 601 of channel A. Therefore, the transmission path variation ofchannel A, namely, (Ia0, Qa0) can be estimated as (I′0, Q′0) based onin-phase component 504 and quadrature-phase component 505, namely, I0and Q0.

[0212] However, the estimation of the transmission path variation ofchannel A, namely, (Ia0, Qa0), is not limited to the case discussedabove, but a pilot symbol of channel A at another time can be used forfinding (Ia0, Qa0) of channel A at time 0.

[0213] In a similar manner to what is discussed above, at time 1, guardsymbol 602 of channel A and pilot symbol 610 of channel B aremultiplexed together. Assume that in-phase component 504 andquadrature-phase component 505 of the reception quadrature basebandsignal are I1 and Q1 respectively, and the transmission path variationof channel A and that of channel B are (Ia1, Qa1) and (Ib1, Qb1)respectively. Since the transmission apparatus transmits 0 (zero) at theguard symbol of channel A, in-phase component 504 and quadrature-phasecomponent 505 of the reception quadrature baseband signal, namely, I1and Q1, are formed of the component of pilot symbol 610 of channel B.Therefore, the transmission path variation of channel B, namely, (Ib1,Qb1) can be estimated as (I′1, Q′1) based on in-phase component 504 andquadrature-phase component 505, namely, I1 and Q1. However, theestimation of the transmission path variation of channel B, namely,(Ib1, Qb1), is not limited to the case discussed above, but a pilotsymbol of channel B at another time can be used for finding (Ib1, Qb1)of channel B at time 1.

[0214] In a similar manner to what is discussed above, at time 6, pilotsymbol 607 of channel A and guard symbol 615 of channel B aremultiplexed together. Assume that in-phase component 504 andquadrature-phase component 505 of the reception quadrature basebandsignal are I6 and Q6 respectively, and the transmission path variationof channel A and that of channel B are (Ia6, Qa6) and (Ib6, Qb6). Sincethe transmission apparatus transmits 0 at the guard symbol of channel B,in-phase component 504 and quadrature-phase component 505 of thereception quadrature baseband signal, namely, I6 and Q6, are formed ofthe component of pilot symbol 607 of channel A.

[0215] Therefore, the transmission path variation of channel A, namely,(Ia6, Qa6) can be estimated as (I′6, Q′6) based on in-phase component504 and quadrature-phase component 505, namely, I6 and Q6. However, theestimation of the transmission path variation of channel A, namely,(Ia6, Qa6), is not limited to the case discussed above, but a pilotsymbol of channel A at another time can be used for finding (Ia6, Qa6)of channel A at time 6.

[0216] In a similar manner to what is discussed above, at time 7, guardsymbol 608 of channel A and pilot symbol 616 of channel B aremultiplexed together. Assume that in-phase component 504 andquadrature-phase component 505 of the reception quadrature basebandsignal are I7 and Q7 respectively, and the transmission path variationof channel A and that of channel B are (Ia7, Qa7) and (Ib7, Qb7). Sincethe transmission apparatus transmits 0 (zero) at the guard symbol ofchannel A, in-phase component 504 and quadrature-phase component 505 ofthe reception quadrature baseband signal, namely, I7 and Q7, are formedof the component of pilot symbol 610 of channel B.

[0217] Therefore, the transmission path variation of channel B, namely,(Ib7, Qb7) can be estimated as (I′7, Q′7) based on in-phase component504 and quadrature-phase component 505, namely, I7 and Q7. However, theestimation of the transmission path variation of channel B, namely,(Ib7, Qb7), is not limited to the case discussed above, but a pilotsymbol of channel B at another time can be used for finding (Ib7, Qb7)of channel B at time 7.

[0218] Assume that the transmission path variations at time 2, time 3,time 4, and time 5 are (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), (Ia5, Qa5).Those values can be found using the estimations discussed above, i.e.(Ia0, Qa0)=(I′0, Q′0), (Ia6, Qa6)=(I′6, Q′6), by, e.g. calculation.However, in order to find (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), and (Ia5,Qa5), pilot symbols at another time of channel A can be used other than(Ia0, Qa0) and (Ia6, Qa6).

[0219] In a similar way to what is discussed above, assume thetransmission path variation at time 2, time 3, time 4, and time 5 are(Ib2, Qb2), (Ib3, Qb3), (Ib4, Qb4), (Ib5, Qb5). Those values can befound using the estimations previously discussed, i.e. (Ib1, Qb1)=(I′1,Q′1), (Ib7, Qb7)=(I′7, Q′7), by, e.g. calculation. However, to fined(Ib2, Qb2), (Ib3, Qb3), (Ib4, Qb4), and (Ib5, Qb5), pilot symbols atanother time of channel B can be used other than (Ib1, Qb1) and (Ib7,Qb7).

[0220] The preparation discussed above allows transmission pathvariation estimation unit 506 of channel A to output, e.g. the foregoing(Ia0, Qa0), (Ia1, Qa1), (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), (Ia5, Qa5),(Ia6, Qa6), and (Ia7, Qa7) as transmission path variation estimationsignals 507 of channel A.

[0221] In a similar way to the case of channel A, transmission pathvariation estimation unit 508 of channel B outputs, e.g. the foregoing(Ib0, Qb0), (Ib1, Qb1), (Ib2, Qb2), (Ib3, Qb3), (Ib4, Qb4), (Ib5, Qb5),(Ib6, Qb6), and (Ib7, Qb7) as transmission path variation estimationsignals 507 of channel A.

[0222] The foregoing description expresses the transmission pathvariation in (I, Q); however, the distortion can be expressed in powerand phase, so that estimation signals 507 and 509 can be expressed inpower and phase.

[0223] In a similar way to what is discussed above, transmission pathvariation estimation unit 518 of channel A receives in-phase component516 and quadrature-phase component 517 of a reception quadraturebaseband signal of a signal received by antenna 513 shown in FIG. 5.Then estimation unit 519 outputs estimation signal 519 of channel A.Estimation unit 520 of channel B outputs estimation signal 520 ofchannel B.

[0224] Signal processor 525 receives the following signals:

[0225] transmission path variation estimation signal 507 of channel A;

[0226] transmission path variation estimation signal 509 of channel B;

[0227] transmission path variation estimation signal 519 of channel A;

[0228] transmission path variation estimation signal 521 of channel B;

[0229] in-phase component 511 and quadrature-phase component 512 ofdelayed reception quadrature baseband signal; and

[0230] in-phase component 530 and quadrature-phase component 531 ofdelayed reception quadrature baseband signal.

[0231] Signal processor 525 carries out matrix calculations with thoseknown signals, so that unknown signals such as a reception quadraturebaseband signal of channel A and that of channel B can be found. Signalprocessor 525 thus outputs those unknown signals as in-phase component526 and quadrature-phase component 527 of the reception quadraturebaseband signal of channel A, and in-phase component 530 andquadrature-phase component 531 of that of channel B. As a result,modulation signals of channels A and B can be demultiplexed from eachother, which allows demodulation.

[0232] In this embodiment, an accuracy of demultiplexing the modulationsignals between channel A and channel B at the reception apparatusdepends on a quality of the pilot symbol received. Thus strongerresistance of the pilot symbol to noise increases the accuracy ofdemultiplexing between the modulation signals of channel A and channelB. As a result, the quality of data received can be improved. The way ofachieving this goal is described hereinafter.

[0233] In FIG. 4, assume that the pilot symbol has amplitude Ap from theorigin, and QPSK has the greatest signal-point amplitude Aq from theorigin. In this status, the relation of Ap>Aq increases the resistanceto noise of the pilot symbol, so that the accuracy of demultiplexing themodulation signals of channel A from those of channel B. As a result,the quality of data received can be improved.

[0234] As shown in FIG. 7, the frame of channel A includes pilot symbols701, 702, and 706, 707. The frame of channel B includes pilot symbol712, 713, and 717, 718. Those pilot symbols are placed in series alongthe time axis, so that the pilot symbols become stronger to noises. Thusthe accuracy of the demultiplexing the modulation signals betweenchannel A and channel B. As a result, the quality of data received isimproved. This is not limited to two symbols in series as shown in FIG.7.

[0235] In this embodiment, the number of channels to be multiplexed aretwo; however, other numbers can be applicable to the embodiment. Theframe structure is not limited to what is shown in FIG. 1, FIG. 6 orFIG. 7. The pilot symbol is taken as an example for demultiplexing thechannels; however, other symbols as long as they are used fordemodulation can be also applicable. In this case, the symbols fordemodulation include, e.g. pilot symbol, unique word, synchronoussymbol, preamble symbol, control symbol, tail symbol, control symbol,known PSK (phase shift keying) modulation symbol, and PSK modulationsymbol added with data.

[0236] A modulation method of the data symbol is not limited to QPSKmodulation, but respective channels can undergo different modulations.On the other hand, all the channels can use the spread spectrumcommunication method. The spread spectrum communication method cancoexist with the other methods.

[0237] The structure of the transmission apparatus of this embodiment isnot limited to what is shown in FIG. 2 or FIG. 3, and when the number ofchannels increase, elements 201 through 208 shown in FIG. 2 are addedaccordingly.

[0238] The structure of the reception apparatus of this embodiment isnot limited to what is shown in FIG. 5, and when the number of channelsincrease, the number of channel estimation units increases accordingly.

[0239] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0240] In this embodiment, the transmission path variation estimationunit of each channel estimates the transmission path variation; however,an estimation of transmission path fluctuation instead of distortion canachieve a similar advantage to what is discussed in this embodiment. Inthis case, a transmission path fluctuation estimation unit forestimating fluctuations of the transmission path is used instead of thedistortion estimation unit. The output signal should be a fluctuationestimation signal accordingly.

[0241] According to the first embodiment discussed above, in atransmission method for transmitting modulation signals of a pluralityof channels to the same frequency band, at the time when a demodulationsymbol is inserted in a channel, in another channel symbol, both of thesame phase signal and a quadrature signal in the in-phase-quadratureplane are made to be zero signals. Use of this method, a transmissionapparatus and a reception apparatus to which this method is applicable,allows the transmission rate of data to increase, and allows thereception apparatus to demultiplex the multiplexed modulation signalwith Oease.

[0242] Exemplary Embodiment 2

[0243] In this second embodiment, a reception apparatus is described.The reception apparatus comprising the following elements:

[0244] a received signal strength intensity estimation unit forestimating a reception received signal strength intensity of a signalreceived by respective antennas and outputting an estimation signal ofthe reception received signal strength intensity of the receptionsignal;

[0245] a phase difference estimation unit for receiving a transmissionpath variation estimation signal of a channel of the respectiveantennas, finding a phase difference of the transmission path variationestimation signal between the respective antennas, and outputting aphase difference signal; and

[0246] a signal selection unit for receiving a reception quadraturebaseband signal of the respective antennas, a transmission pathvariation estimation signal of each channel of the respective antennas,a reception electric field estimation signal of the reception signal,the phase difference signal, then selecting the reception quadraturebaseband signal and the transmission path variation estimation signalfor isolating signals of the respective channels from the receptionsignal, and outputting the signals selected.

[0247] The description refers to the case as an example where thetransmission apparatus shown in FIG. 2 transmits the modulation signalsof the frame structure shown in FIG. 1 demonstrated in the firstembodiment.

[0248]FIG. 8 shows a structure of the reception apparatus in accordancewith the second embodiment. Radio unit 803 of this apparatus receivessignal 802 received by antenna 801, and outputs in-phase component 804and quadrature-phase component 805 of the reception quadrature basebandsignal.

[0249] Transmission path variation estimation unit 806 of channel Areceives in-phase component 804 and quadrature-phase component 805 ofthe reception quadrature baseband signal. Then estimation unit 806operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 807 of channel A.

[0250] Transmission path variation estimation unit 808 of channel Breceives in-phase component 804 and quadrature-phase component 805 ofthe reception quadrature baseband signal. Then estimation unit 808operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 809 of channel B.

[0251] Delay unit 810 receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal, and outputs in-phase component 811 and quadrature-phasecomponent 812 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 807 and 809 of channel A and channel B.

[0252] Radio unit 815 receives signal 814 received by antenna 813, andoutputs in-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal.

[0253] Transmission path variation estimation unit 818 of channel Areceives in-phase component 816 and quadrature-phase component 817 ofthe reception quadrature baseband signal. Then estimation unit 818operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 819 of channel A.

[0254] Transmission path variation estimation unit 820 of channel Breceives in-phase component 816 and quadrature-phase component 817 ofthe reception quadrature baseband signal. Then estimation unit 820operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 821 of channel B.

[0255] Delay unit 822 receives in-phase component 816 andquadrature-phase component 817 of the reception quadrature basebandsignal, and outputs in-phase component 823 and quadrature-phasecomponent 824 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 819 and 821 of channel A and channel B.

[0256] Radio unit 827 receives signal 826 received by antenna 825, andoutputs in-phase component 828 and quadrature-phase component 829 ofreception quadrature baseband signal.

[0257] Transmission path variation estimation unit 830 of channel Areceives in-phase component 828 and quadrature-phase component 829 ofthe reception quadrature baseband signal. Then estimation unit 830operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 831 of channel A.

[0258] Transmission path variation estimation unit 832 of channel Breceives in-phase component 828 and quadrature-phase component 829 ofthe reception quadrature baseband signal. Then estimation unit 832operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 833 of channel B.

[0259] Delay unit 834 receives in-phase component 828 andquadrature-phase component 829 of the reception quadrature basebandsignal, and outputs in-phase component 835 and quadrature-phasecomponent 836 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 831 and 833 of channel A and channel B.

[0260] Radio unit 839 receives signal 838 received by antenna 837, andoutputs in-phase component 840 and quadrature-phase component 841 ofreception quadrature baseband signal.

[0261] Transmission path variation estimation unit 842 of channel Areceives in-phase component 840 and quadrature-phase component 841 ofthe reception quadrature baseband signal. Then estimation unit 842operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 843 of channel A.

[0262] Transmission path variation estimation unit 844 of channel Breceives in-phase component 840 and quadrature-phase component 841 ofthe reception quadrature baseband signal. Then estimation unit 844operates, e.g. in a similar way to estimation unit 506 of channel Ashown in FIG. 5 of the first embodiment, and outputs transmission pathvariation estimation signal 845 of channel B.

[0263] Delay unit 846 receives in-phase component 840 andquadrature-phase component 841 of the reception quadrature basebandsignal, and outputs in-phase component 847 and quadrature-phasecomponent 848 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 843 and 845 of channel A and channel B.

[0264] Received signal strength intensity estimation unit 849 receivesreception signals 802, 814, 826, 838, then estimates the receptionreceived signal strength intensity of the foregoing respective signals,and outputs the estimated values as reception received signal strengthintensity estimation signal 850.

[0265] Phase difference estimation unit 851 receives transmission pathvariation estimation signals 807, 819, 831, 843 of channel A, then findsrespective phase differences such as a phase difference between signals807 and 819 in the in-phase-quadrature plane, and outputs the phasedifference as phase difference estimation signal 852 of channel A.

[0266] In a similar way to what is done by estimation unit 851, phasedifference estimation unit 853 receives transmission path variationestimation signals 809, 821, 833, 845 of channel B, then findsrespective phase differences such as a phase difference between signals809 and 821 in the in-phase-quadrature plane, and outputs the phasedifference as phase difference estimation signal 854 of channel B.

[0267] Signal selection unit 855 receives the following signals:

[0268] transmission path variation estimation signal 807 of channel A;

[0269] transmission path variation estimation signal 809 of channel B;

[0270] in-phase component 811 and quadrature-phase component 812 ofdelayed reception quadrature baseband signal;

[0271] transmission path variation estimation signal 819 of channel A;

[0272] transmission path variation estimation signal 821 of channel B;

[0273] in-phase component 823 and quadrature-phase component 824 ofdelayed reception quadrature baseband signal;

[0274] transmission path variation estimation signal 831 of channel A;

[0275] transmission path variation estimation signal 833 of channel B;

[0276] in-phase component 835 and quadrature-phase component 836 ofdelayed reception quadrature baseband signal;

[0277] transmission path variation estimation signal 843 of channel A;

[0278] transmission path variation estimation signal 845 of channel B;

[0279] in-phase component 847 and quadrature-phase component 848 ofdelayed reception quadrature baseband signal;

[0280] received signal strength intensity estimation signal 850;

[0281] phase difference estimation signal 852 of channel A; and

[0282] phase difference estimation signal 854 of channel B;

[0283] Then signal selection unit 855 selects a group of signalssupplied from the antenna, which can most accurately demultiplex channelA signals from channel B signals, out of received signal strengthintensity estimation signal 850, phase difference estimation signal 852of channel A, and phase difference estimation signal 854 of channel B.Signal selection unit 855 outputs signal groups 856 and 857.

[0284] The signal group here refers to, e.g. transmission path variationestimation signal 807 and estimation signal 809 of channel B estimatedfrom the signal received by antenna 801, in-phase component 811 andquadrature-phase component 812 of the delayed reception quadraturebaseband signal.

[0285] Signal processor 858 receives signal groups 856, 857, andoperates in a similar way to signal processor 525 shown in FIG. 5 of thefirst embodiment. Signal processor 858 outputs in-phase component 859,quadrature-phase component 860 of the reception quadrature basebandsignal of channel A as well as in-phase component 861, quadrature-phasecomponent of the reception quadrature baseband signal 862 of channel B.

[0286] Demodulator 863 receives in-phase component 859 andquadrature-phase component 860 of the reception quadrature basebandsignal of channel A, and outputs reception digital signal 864 of channelA.

[0287] Demodulator 865 receives in-phase component 861 andquadrature-phase component 862 of the reception quadrature basebandsignal of channel B, and outputs reception digital signal 866 of channelB.

[0288]FIG. 9 shows a structure of the reception apparatus in accordancewith the second embodiment, and the elements operating in a similar wayto those shown in FIG. 8 have the same reference marks.

[0289] Received signal strength intensity estimation unit 901 receivesthe following signals:

[0290] in-phase component 804 and quadrature-phase component 805 of thereception quadrature baseband signal;

[0291] in-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal:

[0292] in-phase component 828 and quadrature-phase component 829 of thereception quadrature baseband signal; and

[0293] in-phase component 840 and quadrature-phase component 841 of thereception quadrature baseband signal.

[0294] Then estimation unit 901 estimates the reception received signalstrength intensity of the foregoing respective components, and outputsreception received signal strength intensity estimation signal 850.

[0295]FIG. 10 shows transmission path variationestimation signals of achannel in accordance with the second embodiment. The following foursignals are mapped in FIG. 10:

[0296] transmission path variation estimation signal 1001 of a channelof a signal received by antenna 801, and expressed in (I801, Q801);

[0297] transmission path variation estimation signal 1002 of a channelof a signal received by antenna 813, and expressed in (I813, Q813);

[0298] transmission path variation estimation signal 1003 of a channelof a signal received by antenna 825, and expressed in (I825, Q825);

[0299] transmission path variation estimation signal 1004 of a channelof a signal received by antenna 837, and expressed in (I837, Q837);

[0300] Next, an operation of the reception apparatus, in particular ofphase difference estimation unit 851 and signal selection unit 855, isdemonstrated hereinafter with reference to FIGS. 8 and 10.

[0301] Assume that phase difference estimation unit 851 receives signal1001, signal 1002, signal 1003 and signal 1004 in FIG. 10 astransmission path variation estimation signals 807, 819, 831, and 843 ofchannel A respectively. In this case, find the phase difference between(I801, Q801) and (I813, Q813) in I-Q plane. In a similar way to this,find the phase difference between the following combinations in I-Qplane: (I801, Q801) and (I825, Q825); (I801, Q801) and (I837, Q837);(I813, Q813) and (I825, Q825); (I813, Q813) and (I837, Q837). Then phasedifference estimation unit 851 outputs phase difference estimationsignal 852 of channel A. Phase difference estimation unit 853 outputsphase difference estimation signal 854 of channel B in a similar way towhat is discussed above.

[0302] Next, an operation of signal selection unit 855 is demonstrated:Phase difference estimation signal 852 of channel A takes a valueranging from 0 to pi (π). In other words, the foregoing respective phasedifferences between (I801, Q801) and (I813, Q813); (I801, Q801) and(I825, Q825); (I801, Q801) and (I837, Q837); (I813, Q813) and (I825,Q825); (I813, Q813) and (1837, Q837) take a value ranging from 0 to pi(π). For instance, assume that the phase difference between (I801, Q801)and (I813, Q813) is θ, find an absolute value of θ, and find absolutevalues of each one of the phase differences.

[0303] In a similar way, determine whether or not phase differenceestimation signal 854 of channel B has correlation.

[0304] Signal selection unit 855 selects an optimum antenna 2 system outof phase difference estimation signals 852, 854 of channels A, Bsupplied. A method of this selection is demonstrated hereinafter.

[0305] For instance, assume that a phase difference of channel A ofsignals received by antenna 801 and antenna 813 is 0 (zero) and that ofchannel B is also 0. At this time, it is prepared that the signalsreceived by antennas 801 and 813 should not be selected as signal groups856, 857. On the other hand, assume that a phase difference of channel Aof signals received by antenna 801 and antenna 813 is 0 (zero) and thatof channel B is pi (π). At this time, it is prepared that the signalsreceived by antennas 801 and 813 should be selected as signal groups856, 857.

[0306] Place signal 802 received by antenna 801, signal 814 by antenna813, signal 826 by antenna 825, and signal 838 by antenna 837 indescending order of reception received signal strength intensity withreceived signal strength intensity estimation signal 850. Then selectthe signals having stronger electric field intensities as signal groups856, 857.

[0307] As such, optimum signal groups are selected on a priority baseusing a phase difference or a reception received signal strengthintensity, then the selected ones are output as signal groups 856, 857.For instance, the phase difference between a transmission path variationof channel A of antenna 801 and that of antenna 813 does not correlatewith the phase difference between a transmission path variation ofchannel B of antenna 801 and that of antenna 813. The reception receivedsignal strength intensity of antenna 801 and that of antenna 813 arestronger than those of other antennas. Then transmission path variationestimation signal 807 of channel A, variation estimation signal 809 ofchannel B, in-phase component 811 and quadrature-phase component 812 ofthe delayed reception orthogonal are output as signal group 856.Transmission path variation estimation signal 819 of channel A,variation estimation signal 821 of channel B, in-phase component 823 andquadrature-phase component 824 of the delayed reception orthogonal areoutput as signal group 857.

[0308]FIG. 9 has a structure of the received signal strength intensityestimation unit different from that shown in FIG. 8. Reception electricfield estimation unit 901 of FIG. 9 differs from that of FIG. 8 in thefollowing point: Estimation unit 901 finds reception received signalstrength intensity from in-phase component 804 and quadrature-phasecomponent 805 of the reception quadrature baseband signal. In a similarmanner, estimation unit 901 finds the respective field intensity fromin-phase component 816 and quadrature-phase component 817, from in-phasecomponent 828 and quadrature-phase component 829, and from in-phasecomponent 840 and quadrature-phase component 841.

[0309] In the descriptions discussed above, the frame structure of thetransmission signal shown in FIG. 1 is taken as an example; however,this second embodiment is not limited to the example. Use of twochannels as the number of channels in the descriptions does not limitthis embodiment, and an increase of channels will increase the number oftransmission path variation estimation units. Each channel can undergo adifferent modulation method from each other. On the other hand, all thechannels can use the spread spectrum communication method. The spreadspectrum communication method can coexist with the other methods.

[0310] Not less than four antennas installed in the reception apparatuscan assure the better reception sensitivity. The expression of “antenna”in the previous description does not always mean a single antenna, but“antenna” can mean an antenna unit which is formed of a plurality ofantennas.

[0311] According to the second embodiment discussed above, the receptionapparatus comprises the following elements:

[0312] a received signal strength intensity estimation unit forestimating a reception received signal strength intensity of a signalreceived by respective antennas and outputting an estimation signal ofthe reception received signal strength intensity of the receptionsignal;

[0313] a phase difference estimation unit for receiving a transmissionpath variation estimation signal of a channel of the respectiveantennas, finding a phase difference of the transmission path variationestimation signal, and outputting a phase difference signal; and

[0314] a signal selection unit for receiving a reception quadraturebaseband signal of the respective antennas, a transmission pathvariation estimation signal of each channel of the respective antennas,a reception electric field estimation signal of the reception signal,the phase difference signal, then selecting the reception quadraturebaseband signal and the transmission path variation estimation signalfor demultiplexing signals of the respective channels from the receptionsignal, and outputting the signals selected. The foregoing structureallows the reception apparatus to demultiplex the multiplexed signalswith accuracy.

[0315] Exemplary Embodiment 3

[0316] The third embodiment describes a transmission method, whichhandles the following frame structure of signals transmitted fromrespective antennas:

[0317] a symbol for estimating transmission path variation is insertedinto the frame;

[0318] the symbols is multiplied by a code;

[0319] the symbols of the respective antennas are placed at an identicaltime; and

[0320] the codes of the respective antennas are orthogonal to eachother. The third embodiment also describes a transmission apparatus anda reception apparatus both used in the foregoing transmission method.

[0321]FIG. 11 shows frame structure 1120 in accordance with spreadspectrum communication method A, and frame structure 1130 in accordancewith spread spectrum communication method B. Pilot symbols 1101, 1103,1105 of spread spectrum communication method A are multiplied by a code.Data symbols 1102, 1104 of spread spectrum communication method A aremultiplied by a code.

[0322] Pilot symbols 1106, 1108, 1110 of spread spectrum communicationmethod B are multiplied by a code. Data symbols 1107, 1109 of spreadspectrum communication method B are multiplied by a code.

[0323] Pilot symbol 1101 of communication method A and pilot symbol 1106of communication method B occur at an identical time. In the samemanner, the following combinations occur at an identical time:

[0324] data symbol 1102 of method A and data symbol 1107 of method B;

[0325] pilot symbol 1103 of method A and pilot symbol 1108 of method B;

[0326] data symbol 1104 of method A and data symbol 1109 of method B;and

[0327] pilot symbol 1105 of method A and pilot symbol 1110 of method B

[0328]FIG. 12 shows a structure of the transmission apparatus inaccordance with this third embodiment, and the apparatus comprisestransmission unit 1220 of spread spectrum communication method A,transmission unit 1230 of spread spectrum communication method B, andframe signal generator 1217.

[0329] Transmission unit 1220 of method A is formed of modulation signalgenerator 1202, radio unit 1204, power amplifier 1206, and antenna 1208.Transmission unit 1230 of method B is formed of modulation signalgenerator 1210, radio unit 1212, power amplifier 1214, and antenna 1216.Frame signal generator 1217 outputs the information about the framestructure shown in FIG. 11 as frame signal 1218.

[0330] Modulation signal generator 1202 of method A receivestransmission digital signal 1201 of spread spectrum transmission methodA and frame signal 1218, then outputs modulation signal 1203 of method Ain accordance with the frame structure.

[0331] Radio unit 1204 of method A receives modulation signal 1203, thenoutputs transmission signal 1205 of method A.

[0332] Power amplifier 1206 of method A receives transmission signal1205, amplifies it, then outputs the amplified signal as transmissionsignal 1207 from antenna 1208 in the form of radio wave.

[0333] Modulation signal generator 1210 of method B receivestransmission digital signal 1209 of spread spectrum transmission methodB and frame signal 1218, then outputs modulation signal 1211 of method Bin accordance with the frame structure.

[0334] Radio unit 1212 of method B receives modulation signal 1211, thenoutputs transmission signal 1213 of method B.

[0335] Power amplifier 1214 of method B receives transmission signal1213, amplifies it, then outputs the amplified signal as transmissionsignal 1215 from antenna 1216 in the form of radio wave.

[0336]FIG. 13 shows a structure of modulation signal generators 1202,1210 shown in FIG. 12 of the third embodiment. Pilot symbol modulationsignal generator 1301 receives code Cpa(t) 1302 for a pilot symbol, andmultiplies the pilot symbol by code Cpa(t) 1302, then outputs in-phasecomponent 1303 and quadrature-phase component 1304 of a transmissionquadrature baseband signal of the pilot symbol.

[0337] Primary modulation unit 1306 receives transmission digital signal1305, then outputs in-phase component 1307 and quadrature-phasecomponent 1308 of the quadrature baseband signal of channel 0 undergonethe primary modulation.

[0338] Spread unit 1309 receives in-phase component 1307 andquadrature-phase component 1308 of the quadrature baseband signal ofchannel 0 undergone the primary modulation, code COa(t) 1310 for channel0, frame signal 1320, then multiplies in-phase component 1307,quadrature-phase component 1308 and code C0 a(t) 1310 based on theinformation about frame structure 1320, and outputs in-phase component1311 and quadrature-phase component 1312 of a transmission quadraturebaseband signal of channel 0.

[0339] Primary modulation unit 1313 receives transmission digital signal1305, then outputs in-phase component 1314 and quadrature-phasecomponent 1315 of the quadrature baseband signal of channel 1 undergonethe primary modulation.

[0340] Spread unit 1316 receives in-phase component 1314 andquadrature-phase component 1315 of the quadrature baseband signal ofchannel 1 undergone the primary modulation, code C1 a(t) 1317 forchannel 1, frame signal 1320, then multiplies in-phase component 1314,quadrature-phase component 1315 and code C1 a(t) 1317 based on theinformation about the frame structure 1320, and outputs in-phasecomponent 1318 and quadrature-phase component 1319 of a transmissionquadrature baseband signal of channel 1.

[0341] Adding unit 1321 receives in-phase component 1311 of thetransmission quadrature baseband signal of channel 0 and in-phasecomponent 1318 of that of channel 1, and adds component 1311 andcomponent 1318 together, then outputs the added in-phase component 1322.

[0342] Adding unit 1323 receives quadrature-phase component 1312 of thetransmission quadrature baseband signal of channel 0 and in-phasecomponent 1319 of that of channel 1, and adds component 1312 andcomponent 1319 together, then outputs the added quadrature-phasecomponent 1324.

[0343] In-phase component switcher 1325 receives in-phase component 1303of the pilot symbol transmission quadrature baseband signal 1303, addedin-phase component 1322 and frame signal 1320, then selects in-phasecomponent 1303 and added in-phase component 1322 based on theinformation about frame structure 1320, and outputs in-phase component1326 of the selected transmission quadrature baseband signal.

[0344] Quadrature-phase component switcher 1327 receivesquadrature-phase component 1304 of the pilot symbol transmissionquadrature baseband signal, added quadrature-phase component 1324 andframe signal 1320, then selects quadrature-phase component 1304 andadded quadrature-phase component 1324 based on the information aboutframe structure 1320, and outputs quadrature-phase component 1328 of theselected transmission quadrature baseband signal.

[0345] Orthogonal modulation unit 1329 receives in-phase component 1326and quadrature-phase component 1328 of the selected transmissionquadrature baseband signal, then provides the input with orthogonalmodulation, and outputs modulation signal 1330.

[0346]FIG. 14 shows a relation between a pilot symbol and a code to bemultiplied to the pilot symbols in pilot-symbol structure 1420 ofspread-spectrum communication method A and in pilot-symbol structure1430 of method B. Spread code 1401 of method A at time 0 is expressed asCpa(0), and spread code 1402 of method A at time 1 is expressed asCpa(1). The following codes are expressed in the same manner:

[0347] code 1403 pf method A at time 2 as Cpa(2);

[0348] code 1404 of method A at time 3 as Cpa(3);

[0349] code 1405 of method A at time 4 as Cpa(4);

[0350] code 1406 of method A at time 5 as Cpa(5);

[0351] code 1407 of method A at time 6 as Cpa(6); and

[0352] code 1408 of method A at time 7 as Cpa(7).

[0353] Time 0-time 7 form one cycle of spread code Cpa.

[0354] In a similar manner to the spread codes of method A, spread codesof method B are expressed as follows:

[0355] code 1409 of method B at time 0 as Cpb(0);

[0356] code 1410 of method B at time 1 as Cpb(1);

[0357] code 1411 of method B at time 2 as Cpb(2);

[0358] code 1412 of method B at time 3 as Cpb(3);

[0359] code 1413 of method B at time 4 as Cpb(4);

[0360] code 1414 of method B at time 5 as Cpb(5);

[0361] code 1415 of method B at time 6 as Cpb(6); and

[0362] code 1416 of method B at time 7 as Cpb(7).

[0363] Time 0-time 7 form one cycle of spread code Cpb.

[0364]FIG. 15 shows a structure of the reception apparatus in accordancewith the third embodiment. The elements operating in the same way asthose in FIG. 5 have the same reference marks.

[0365] Transmission path variation estimation unit 1501 ofspread-spectrum communication method A receives in-phase component 504and quadrature-phase component 505 of the reception quadrature basebandsignal. Then estimation unit 1501 estimates transmission-path distortionof method A, and outputs transmission path estimation signal 1502 ofmethod A.

[0366] Transmission path variation estimation unit 1503 ofspread-spectrum communication method B receives in-phase component 504and quadrature-phase component 505 of the reception quadrature basebandsignal. Then estimation unit 1503 estimates transmission-path distortionof method B, and outputs transmission path estimation signal 1504 ofmethod B.

[0367] Transmission path variation estimation unit 1505 ofspread-spectrum communication method A receives in-phase component 516and quadrature-phase component 517 of the reception quadrature basebandsignal. Then estimation unit 1505 estimates transmission-path distortionof method A, and outputs transmission path estimation signal 1506 ofmethod A.

[0368] Transmission path variation estimation unit 1507 ofspread-spectrum communication method B receives in-phase component 516and quadrature-phase component 517 of the reception quadrature basebandsignal. Then estimation unit 1507 estimates transmission-path distortionof method B, and outputs transmission path estimation signal 1508 ofmethod B.

[0369] Signal processor 1509 receives the following signals:

[0370] transmission path variation estimation signal 1502 of method A;

[0371] transmission path variation estimation signal 1504 of method B;

[0372] in-phase component 511 and quadrature-phase component 512 ofdelayed reception quadrature baseband signal;

[0373] transmission path variation estimation signal 1506 of method A;

[0374] transmission path variation estimation signal 1508 of method B;and

[0375] in-phase component 523 and quadrature-phase component 524 ofdelayed reception quadrature baseband signal.

[0376] Then signal processor 1509 outputs the following signals:

[0377] in-phase component 1510 and quadrature-phase component 1511 ofreception quadrature baseband signal of method A; and

[0378] in-phase component 1512 and quadrature-phase component 1513 ofreception quadrature baseband signal of method B.

[0379] Demodulator 1514 of spread spectrum communication method Areceives in-phase component 1510 and quadrature-phase component 1511 ofreception quadrature baseband signal of method A, and outputsreception-digital signal group 1515 of method A.

[0380] Demodulator 1516 of spread spectrum communication method Breceives in-phase component 1512 and quadrature-phase component 1513 ofreception quadrature baseband signal of method B, and outputsreception-digital signal group 1517 of method B.

[0381]FIG. 16 a structure of transmission path variation estimationunits 1501, 1505 of spread-spectrum communication method A anddistortion estimation units 1503, 1507 of method B, both shown in FIG.15.

[0382] Pilot-symbol inverse spread unit 1603 receives in-phase component1601 and quadrature-phase component 1602 of the reception quadraturebaseband signal, and spread-code 1604, and outputs in-phase component1605 and quadrature-phase component 1606 of the pilot symbol of thereception quadrature baseband signal undergone the inverse spread.

[0383] Transmission path variation estimation unit 1607 receivesin-phase component 1605 and quadrature-phase component 1606, and outputstransmission path variation estimation signal 1608.

[0384]FIG. 17 shows frame structure 1710 and transmission path variationamount 1720 along a time axis. Pilot symbol 1701 and transmission pathvariation (I0, Q0) occur at time 0 (zero). In the same manner, followingcombinations occur at respective times:

[0385] pilot symbol 1702 and transmission path variation (I1, Q1) attime 1

[0386] pilot symbol 1703 and transmission path variation (I2, Q2) attime 2

[0387] pilot symbol 1704 and transmission path variation (I3, Q3) attime 3

[0388] pilot symbol 1705 and transmission path variation (I4, Q4) attime 4

[0389] pilot symbol 1706 and transmission path variation (I5, Q5) attime 5

[0390] pilot symbol 1707 and transmission path variation (I6, Q6) attime 6.

[0391] An operation of the transmission apparatus is demonstratedhereinafter with reference to FIG. 11-FIG. 14. Structures of pilotsymbol 1101 of communication method A and pilot symbol 1106 of method B,both occurring at the same time, are described with reference to FIG.14.

[0392]FIG. 14 shows a structure of one pilot symbol. Pilot symbol 1101of spread-spectrum communication method A shown in FIG. 11 is multipliedby code Cpa, and formed of, e.g. spread codes 1401, 1402, 1403, 1404,1405, 1406, 1407, and 1408. In a similar way, pilot symbol 1106 ofspread-spectrum communication method B shown in FIG. 11 is multiplied bycode Cpb, and formed of, e.g. spread codes 1409, 1410, 1411, 1412, 1413,1414, 1415, and 1416. Spread code Cpa multiplied to the pilot symbol ofmethod A is orthogonal to spread code Cpb multiplied to the pilot symbolof method B.

[0393] Next, the operation of the transmission apparatus isdemonstrated. In FIG. 12, frame signal generator 1217 outputs theinformation about the frame structure shown in FIG. 11 as frame signal1218. Modulation signal generator 1202 of method A receives transmissiondigital signal 1201 of spread spectrum transmission method A and framesignal 1218, then outputs modulation signal 1203 of method A inaccordance with the frame structure. Modulation signal generator 1210 ofmethod B receives transmission digital signal 1209 of spread spectrumtransmission method B and frame signal 1218, then outputs modulationsignal 1211 of method B in accordance with the frame structure.

[0394] Operations of modulation signal generators 1202 and 1210 aredemonstrated with reference to FIG. 13. At a transmitter ofspread-spectrum communication method A, pilot-symbol transmission signalgenerator 1301 shown in FIG. 13 receives code 1302 for the pilot symboland frame signal 1320. Then generator 1301 outputs, e.g. in-phasecomponent 1303 and quadrature-phase component 1304 of a pilot symboltransmission quadrature baseband signal in accordance with the structureof the pilot symbol of communication method A shown in FIG. 14.

[0395] In a similar way to the foregoing transmitter, at a transmitterof spread-spectrum communication method B, pilot-symbol transmissionsignal generator 1301 shown in FIG. 13 receives code 1302 for the pilotsymbol and frame signal 1320. Then generator 1301 outputs, e.g. in-phasecomponent 1303 and quadrature-phase component 1304 of a pilot symboltransmission quadrature baseband signal in accordance with the structureof the pilot symbol of communication method B shown in FIG. 14.

[0396] As such, the pilot symbol of communication method A is orthogonalto the spread code of the pilot symbol of communication method B.

[0397] Next, an operation of the reception apparatus is demonstratedwith reference to FIG. 15-FIG. 17. Antenna 501 shown in FIG. 15 receivessignal 502 in which spread-spectrum communication methods A and B aremixed, and radio unit 503 outputs in-phase component 504 andquadrature-phase component 505, in which methods A and B are mixed, of areception quadrature baseband signal.

[0398] Operations of transmission path variation estimation unit 1501 ofmethod A and estimation unit 1503 of method B are demonstrated withreference to FIG. 16. Estimation unit 1501 of method A operates asfollows: Pilot-symbol inverse-spread unit 1603 in FIG. 16 receivesin-phase component 1601 and quadrature-phase component 1602 of thereception quadrature baseband signal, in which methods A and B aremixed, and spread code 1604 for the pilot symbol of method A. Theninverse-spread unit 1603 detects pilot symbols in in-phase component1601 and quadrature-phase component 1602, and provides the detectedpilot symbols with the inverse-spread using spread-code 1604. Finally,inverse-spread unit 1603 outputs in-phase component 1605 andquadrature-phase component 1606 undergone the inverse spread.

[0399] In the foregoing operation, the component of method B in thepilot symbol of in-phase component 1601 and quadrature-phase component1602 can be removed by the inverse-spread because the code of method Ais orthogonal to the code of method B.

[0400] Transmission path variation estimation unit 1607 is describedwith reference to FIG. 17. Transmission path variations (I0, Q0) and(I6, Q6) of the pilot symbol in FIG. 17 are found using in-phasecomponent 1605 and quadrature-phase component 1606 of the receptionquadrature baseband signal of the pilot symbol undergone theinverse-spread. Then transmission path variations (I1, Q1), (I2, Q2),(I3, Q3), (I4, Q4), and (I5, Q5) of data symbol are found usingdistortions (I0, Q0) and (I6, Q6) of the pilot symbol. Those distortionsare output as transmission path variation estimation signal 1608.

[0401] In a similar way to what is discussed above, transmission pathvariation estimation unit 1503 of method B outputs estimation signal1504 from reception signal 502 in which methods A and B are mixed.Distortion estimation unit 1505 of method A and estimation unit 1507 ofmethod B output transmission variation estimation signal 1506 of methodA and estimation signal 1508 of method B respectively from receptionsignal 514 in which methods A and B are mixed.

[0402] In the foregoing descriptions, the transmission path variation isexpressed in (I, Q); however the distortion can be expressed in power orphase, so that the distortions expressed in power and phase can beoutput as variation estimation signals 1502, 1506 of method A, andsignals 1506, 1508 of method B.

[0403] The structures and operations discussed above allowdemultiplexing the modulation signals of spread-spectrum communicationmethod A from those of method B, so that the signals can be demodulated.

[0404] In this embodiment, an accuracy of demultiplexing the modulationsignals between channel A and channel B at the reception apparatusdepends on a quality of the pilot symbol received. Thus strongerresistance of the pilot symbol to noise increases the accuracy ofdemultiplexing the modulation signals of channel A from channel B. As aresult, the quality of data received can be improved. A greatertransmission power to the pilot symbols than that to the data symbolsincreases the noise resistance of the pilot symbols, so that theaccuracy of demultiplexing the modulation signals of spread-spectrumcommunication method A from method B increases. As a result, the qualityof reception data can be improved.

[0405] In this third embodiment, two methods of spread-spectrumcommunication methods are multiplexed; however, the present invention isnot limited to two methods. The present invention is not limited to theframe structures shown in FIGS. 11, 14, and 16. The transmission pathvariation can be estimated using the pilot symbol as an example; howeverother symbols can be used for this purpose as long as they can estimatedistortions. Spread-spectrum communication methods A and B use twochannels for multiplexing; however, it is not limited to two channelsonly.

[0406] The structure of the transmission apparatus in accordance withthe third embodiment is not limited to what is shown in FIG. 12 or FIG.13, and when the number of spread-spectrum communication methodsincreases, the number of sections formed of elements 1201-1208 shown inFIG. 12 increases accordingly. When the number of channels increases,the number of sections formed of elements 1306 and 1309 shown in FIG. 13increases accordingly.

[0407] The structure of the reception apparatus in accordance with thethird embodiment is not limited to what is shown in FIG. 15, and whenthe number of spread-spectrum communication methods increases, thenumber of distortion estimation units increases accordingly.

[0408] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0409] According to the third embodiment discussed above, thetransmission method handles the following frame structure of a signaltransmitted from respective antenna:

[0410] a symbol for estimating transmission path variation is insertedinto the frame;

[0411] the symbol is multiplied by a code;

[0412] the symbols of the respective antennas are arranged at anidentical time; and

[0413] the codes of the respective antennas are orthogonal to eachother.

[0414] The third embodiment also uses the transmission apparatus and thereception apparatus in the foregoing transmission method. In thissystem, multiplexing modulation signals of a plurality of channels tothe same frequency band increases the data transmission rate, and allowsthe reception apparatus to demultiplex the multiplexed modulation signalwith ease.

[0415] Exemplary Embodiment 4

[0416] The fourth exemplary embodiment demonstrates a receptionapparatus comprising the following elements:

[0417] a received signal strength intensity estimation unit forreceiving a modulation signal of a spread-spectrum communication methodtransmitted to the same frequency band from respective transmissionantennas, then estimating a reception received signal strength intensityof the signal received by respective antennas, and outputting anestimation signal of the reception received signal strength intensity ofthe reception signal;

[0418] a phase difference estimation unit for receiving a transmissionpath variation estimation signal of a spread-spectrum communicationmethod of the respective antennas, finding a phase difference of thetransmission path variation estimation signals of the spread-spectrumcommunication method between the respective antennas, and outputting aphase difference signal; and

[0419] a signal selection unit for receiving a reception quadraturebaseband signal of the respective antennas, the transmission pathvariation estimation signals of respective spread-spectrum communicationmethods of the respective antennas, the reception received signalstrength intensity estimation signal of the reception signal, the phasedifference signal, then selecting the reception quadrature basebandsignal and the transmission path variation estimation signal forisolating signals of the respective methods from the reception signal,and outputting the signals selected.

[0420] The description of this fourth embodiment takes the case as anexample, where the modulation signal having the frame structure shown inFIG. 11 is transmitted by the transmission apparatus shown in FIG. 12and used in the third exemplary embodiment.

[0421]FIG. 18 shows a structure of a reception apparatus in accordancewith the fourth embodiment. The elements operating in a similar way tothose in FIG. 8 have the same reference marks.

[0422] Transmission path variation estimation unit 1801 ofspread-spectrum communication method A receives in-phase component 804and quadrature-phase component 805 of the reception quadrature basebandsignal. Then estimation unit 1801 operates, e.g. in a similar way toestimation unit 1501 of method A shown in FIG. 15 of the thirdembodiment, and outputs transmission path variation estimation signal1802 of method A.

[0423] Transmission path variation estimation unit 1803 ofspread-spectrum communication method B receives in-phase component 804and quadrature-phase component 805 of the reception quadrature basebandsignal. Then estimation unit 1803 operates, e.g. in a similar way toestimation unit 1501 of method A shown in FIG. 15 of the thirdembodiment, and outputs transmission path variation estimation signal1804 of method B.

[0424] Delay unit 1805 receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal, and outputs in-phase component 1806 and quadrature-phasecomponent 1807 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 1802 and 1804 of method A and method B.

[0425] Transmission distortion estimation unit 1808 of method A receivesin-phase component 804 and quadrature-phase component 805 of thereception quadrature baseband signal. Then estimation unit 1808operates, e.g. in a similar way to estimation unit 1501 of the samemethod A shown in FIG. 15 of the third embodiment, and outputstransmission path variation estimation signal 1809 of method A.

[0426] Transmission path variation estimation unit 1810 of method Breceives in-phase component 804 and quadrature-phase component 805 ofthe reception quadrature baseband signal. Then estimation unit 1810operates, e.g. in a similar way to estimation unit 1501 of method Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1811 of method B.

[0427] Delay unit 1812 receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal, and outputs in-phase component 1813 and quadrature-phasecomponent 1814 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 1809 and 1811 of method A and method B.

[0428] Transmission distortion estimation unit 1815 of method A receivesin-phase component 804 and quadrature-phase component 805 of thereception quadrature baseband signal. Then estimation unit 1815operates, e.g. in a similar way to estimation unit 1501 of channel Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1816 of method A.

[0429] Transmission path variation estimation unit 1817 of method Breceives in-phase component 804 and quadrature-phase component 805 ofthe reception quadrature baseband signal. Then estimation unit 1817operates, e.g. in a similar way to estimation unit 1501 of method Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1818 of method B.

[0430] Delay unit 1819 receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal, and outputs in-phase component 1820 and quadrature-phasecomponent 1821 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 1816 and 1818 of method A and method B.

[0431] Transmission distortion estimation unit 1822 of method A receivesin-phase component 804 and quadrature-phase component 805 of thereception quadrature baseband signal. Then estimation unit 1822operates, e.g. in a similar way to estimation unit 1501 of method Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1823 of method A.

[0432] Transmission path variation estimation unit 1824 of method Breceives in-phase component 804 and quadrature-phase component 805 ofthe reception quadrature baseband signal. Then estimation unit 1824operates, e.g. in a similar way to estimation unit 1501 of channel Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1825 of method B.

[0433] Delay unit 1826 receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal, and outputs in-phase component 1827 and quadrature-phasecomponent 1828 of the reception quadrature baseband signal which delaysby the time needed for obtaining transmission path variation estimationsignals 1823 and 1825 of method A and method B.

[0434] Phase difference estimation unit 1829 receives transmission pathvariation estimation signals 1802, 1809, 1816, 1823 of method A, thenfinds respective phase differences such as a phase difference betweensignals 1802 and 1809 in the in-phase-quadrature plane, and outputs thephase difference as phase difference estimation signal 1830 of method A.

[0435] In a similar way to what is done by estimation unit 1829, phasedifference estimation unit 1831 receives transmission path variationestimation signals 1804, 1811, 1818, 1825 of method B, then findsrespective phase differences such as a phase difference between signals1804 and 1811 in the in-phase-quadrature plane, and outputs the phasedifferences as phase difference estimation signal 1832 of method B.

[0436] Signal selection unit 1833 receives the following signals:

[0437] transmission path variation estimation signal 1802 of method A;

[0438] transmission path variation estimation signal 1804 of method B;

[0439] in-phase component 1806 and quadrature-phase component 1807 ofdelayed reception quadrature baseband signal;

[0440] transmission path variation estimation signal 1809 of method A;

[0441] transmission path variation estimation signal 1811 of method B;

[0442] in-phase component 1813 and quadrature-phase component 1814 ofdelayed reception quadrature baseband signal;

[0443] transmission path variation estimation signal 1816 of method A;

[0444] transmission path variation estimation signal 1818 of method B;

[0445] in-phase component 1820 and quadrature-phase component 1821 ofdelayed reception quadrature baseband signal;

[0446] transmission path variation estimation signal 1823 of method A;

[0447] transmission path variation estimation signal 1825 of method B;

[0448] in-phase component 1827 and quadrature-phase component 1828 ofdelayed reception quadrature baseband signal;

[0449] received signal strength intensity estimation signal 850;

[0450] phase difference estimation signal 1830 of method A; and

[0451] phase difference estimation signal 1832 of method B;

[0452] Then signal selection unit 1833 selects a group of signalssupplied from the antenna, which can most accurately isolate method Asignals from method B signals, out of received signal strength intensityestimation signal 850, phase difference estimation signal 1830 of methodA, and phase difference estimation signal 1832 of method B. Signalselection unit 1833 then outputs signal groups 1834 and 1835.

[0453] The signal group here refers to, e.g. transmission path variationestimation signal 1802 of method A, estimation signal 1804 of method B,in-phase component 1806 and quadrature-phase component 1807 of thedelayed reception quadrature baseband signal of the signal received byantenna 801.

[0454] Signal processor 1836 receives signal groups 1834, 1835, andoperates in a similar way to signal processor 1509 shown in FIG. 15 ofthe third embodiment. Signal processor 1836 outputs in-phase component1837, quadrature-phase component 1838 of the reception quadraturebaseband signal of method A as well as in-phase component 1839,quadrature-phase component of the reception quadrature baseband signal1840 of method B.

[0455] Demodulator 1841 of spread-spectrum communication method Areceives in-phase component 1837 and quadrature-phase component 1838 ofthe reception quadrature baseband signal of method A, and outputsreception digital signal 1842 of method A.

[0456] Demodulator 865 of spread-spectrum communication method Breceives in-phase component 1839 and quadrature-phase component 1840 ofthe reception quadrature baseband signal of method B, and outputsreception digital signal 1844 of method B.

[0457]FIG. 19 shows a structure of the reception apparatus in accordancewith this exemplary embodiment, and the elements operating in a similarway to those shown in FIGS. 8, 18 have the same reference marks.

[0458]FIG. 10 shows transmission path variation estimation signals of aspread-spectrum communication method in accordance with the fourthembodiment. The following four signals are mapped in FIG. 10:

[0459] transmission path variation estimation signal 1001 of a signal ofa spread-spectrum communication method received by antenna 801, andexpressed in (I801, Q801);

[0460] transmission path variation estimation signal 1002 of a signal ofa spread-spectrum communication method received by antenna 813, andexpressed in (I813, Q813);

[0461] transmission path variation estimation signal 1003 of a signal ofa spread-spectrum communication method received by antenna 825, andexpressed in (I825, Q825);

[0462] transmission path variation estimation signal 1004 of a signal ofa spread-spectrum method received by antenna 837, and expressed in(I837, Q837);

[0463] Next, an operation of the reception apparatus, in particularoperations of phase difference estimation unit 1829 and signal selectionunit 1831, is demonstrated hereinafter with reference to FIGS. 1 and 18.

[0464] Assume that phase difference estimation unit 1829 receives signal1001, signal 1002, signal 1003 and signal 1004 shown in FIG. 10 astransmission path variation estimation signals 1802, 1809, 1816, and1823 of method A respectively. In this case, find the phase differencebetween (I801, Q801) and (I813, Q813) in I-Q plane. In a similar way tothis, find the phase difference between the following combinations inI-Q plane: (I801, Q801) and (I825, Q825); (I801, Q801) and (I837, Q837);(I813, Q813) and (I825, Q825); (I813, Q813) and (I837, Q837). Then phasedifference estimation unit 851 outputs phase difference estimationsignal 852 of method A. Phase difference estimation unit 1831 outputsphase difference estimation signal 1832 of method B in a similar way towhat is discussed above.

[0465] Next, an operation of signal selection unit 1833 is demonstrated:Phase difference estimation signal 1830 of method A takes a valueranging from 0 to pi (π). In other words, the foregoing respective phasedifferences between (I801, Q801) and (I813, Q813); (I801, Q801) and(I825, Q825); (I801, Q801) and (I837, Q837); (I813, Q813) and (I825,Q825); (I813, Q813) and (I837, Q837) take a value ranging from 0 to pi(π). For instance, assume that the phase difference between (I801, Q801)and (I813, Q813) is θ, find an absolute value of θ, and find absolutevalues of each one of the phase differences.

[0466] In a similar way, determine whether or not phase differenceestimation signal 1832 of method B has correlation.

[0467] Signal selection unit 1833 selects optimum antenna system 2 basedon phase difference estimation signals 1830, 1832 of spread-spectrumcommunication methods A, B supplied. A method of this selection isdemonstrated hereinafter.

[0468] For instance, assume that a phase difference of method A ofsignals received by antenna 801 and antenna 813 is 0 (zero) and that ofmethod B is also 0. At this time, it is prepared that the signalsreceived by antennas 801 and 813 should not be selected as signal groups856, 857. On the other hand, assume that a phase difference of method Aof signals received by antenna 801 and antenna 813 is 0 (zero) and thatof method B is pi (π). At this time, it is prepared that the signalsreceived by antennas 801 and 813 should be selected as signal groups1834, 1835.

[0469] Place signal 802 received by antenna 801, signal 814 by antenna813, signal 826 by antenna 825, and signal 838 by antenna 837 indescending order of reception received signal strength intensity withelectric field estimation signal 850, then select the signals havingstronger received signal strength intensity as signal groups 856, 857.

[0470] As such, optimum signal groups are selected on a priority baseusing a phase difference or a reception received signal strengthintensity, then the selected ones are output as signal groups 1834,1835. For instance, the phase difference between a transmission pathvariation of method A of antenna 801 and that of antenna 813 does notcorrelate with the phase difference between a transmission pathvariation of method B of antenna 801 and that of antenna 813. Thereception received signal strength intensity of antenna 801 and that ofantenna 813 are stronger than those of other antennas. Then transmissionpath variation estimation signal 1802 of method A, variation estimationsignal 1804 of method B, in-phase component 1806 and quadrature-phasecomponent 1807 of the delayed reception orthogonal are output as signalgroup 1834. Transmission path variation estimation signal 1809 of methodA, variation estimation signal 1811 of method B, in-phase component 1813and quadrature-phase component 1814 of the delayed reception orthogonalare output as signal group 1835.

[0471]FIG. 19 shows a structure of the received signal strengthintensity estimation unit different from that shown in FIG. 18.Reception received signal strength intensity estimation unit 901 of FIG.19 differs from that of FIG. 18 in the following point: Estimation unit901 finds reception received signal strength intensity from in-phasecomponent 804 and quadrature-phase component 805 of the receptionquadrature baseband signal. In a similar manner, estimation unit 901finds the respective field intensity from in-phase component 816 andquadrature-phase component 817, from in-phase component 828 andquadrature-phase component 829, and from in-phase component 840 andquadrature-phase component 841.

[0472] In the descriptions discussed above, the frame structure of thetransmission signal shown in FIG. 11 is taken as an example; however,this embodiment is not limited to the example. Use of twospread-spectrum communication methods as the number of communicationmethods in the descriptions does not limit this embodiment, and anincrease of the methods will increase the number of transmission pathvariation estimation units. Method A and method B undergo multiplexingof two channels; however, the present invention is not limited totwo-channels.

[0473] Not less than four antennas installed in the reception apparatusassure the better reception sensitivity. The expression of “antenna” inthe previous description does not always mean a single antenna, but“antenna” can mean an antenna unit which is formed of a plurality ofantennas.

[0474] As discussed above, the fourth exemplary embodiment has referredto the reception apparatus comprising the following elements:

[0475] a received signal strength intensity estimation unit forreceiving a modulation signal of a spread-spectrum communication methodtransmitted to the same frequency band from respective transmissionantennas, then estimating a reception received signal strength intensityof the signal received by respective antennas, and outputting anestimation signal of the reception received signal strength intensity ofthe reception signal;

[0476] a phase difference estimation unit for receiving a transmissionpath variation estimation signal of a spread-spectrum communicationmethod of the respective antennas, finding a phase difference of thetransmission path variation estimation signal of the spread-spectrumcommunication method between the respective antennas, and outputting aphase difference signal; and a signal selection unit for receiving areception quadrature baseband signal of the respective antennas, atransmission path variation estimation signal of respectivespread-spectrum communication methods of the respective antennas, areception electric field estimation signal of the reception signal, andthe phase difference signal, then selecting the reception quadraturebaseband signal and the transmission path variation estimation signalfor isolating signals of the respective methods from the receptionsignal, and outputting the signals selected. The foregoing structureallows the reception apparatus to demultiplex a multiplexed signal withaccuracy.

[0477] Exemplary Embodiment 5

[0478] The fifth exemplary embodiment describes the transmission methodof transmitting modulation signals of a plurality of channels from aplurality of antennas to the same frequency band. More particularly, ademodulation symbol to be inserted into a channel is formed of aplurality of sequential symbols, and each one of demodulation symbols ofrespective channels is placed at the same time and orthogonal to eachother. The fifth embodiment also describes a transmission apparatus anda reception apparatus to be used in the foregoing transmission method.

[0479]FIG. 20 shows frame structure 2020 of channel A and framestructure 2030 of channel B along a time axis. Frame structure 2020includes pilot symbols 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009,and data symbol 2005. Frame structure 2030 includes pilot symbols 2010,2011, 2012, 2013, 2015, 2016, 2017, 2018, and data symbol 2014.

[0480]FIG. 21 shows a placement of signal points of the pilot symbols ofchannels A and B in in-phase-quadrature (I-Q) plane, and signal points2101 and 2102 indicate the pilot symbols.

[0481]FIG. 2 shows a structure of the transmission apparatus inaccordance with the fifth embodiment.

[0482]FIG. 22 shows a detailed structure of modulation signal generators202, 212. Data-symbol modulation signal generator 2202 receivestransmission digital signal 2201, frame signal 2208. When frame signal2208 indicates a data symbol, generator 2202 provides signals 2201 with,e.g. QPSK modulation, and outputs in-phase component 2203 andquadrature-phase component 2204 of a transmission quadrature basebandsignal of the data symbol.

[0483] Pilot symbol modulation signal generator 2205 receives framesignal 2208. When signal 2208 indicates a pilot symbol, generator 2205outputs in-phase component 2206 and quadrature-phase component 2207 of atransmission quadrature baseband signal of the pilot symbol.

[0484] In-phase component switcher 2209 receives in-phase components2203, 2206 and frame signal 2208, then selects the in-phase component oftransmission quadrature baseband signal corresponding to a symbolindicated by frame signal 2208, and outputs the selected one as in-phasecomponent 2210 of the selected transmission quadrature baseband signal.

[0485] Quadrature-phase component switcher 2211 receivesquadrature-phase components 2204, 2207 and frame signal 2208, thenselects a quadrature-phase component of a transmission quadraturebaseband signal corresponding to a symbol indicated by frame signal2208, and outputs the selected one as quadrature-phase component 2212 ofthe selected transmission quadrature baseband signal.

[0486] Orthogonal modulator 2213 receives in-phase component 2210selected, quadrature-phase component 2212 selected, then provides thosecomponents 2210, 2212 with orthogonal modulation, and outputs modulationsignal 2214.

[0487]FIG. 5 shows a structure of the reception apparatus in accordancewith this fifth embodiment.

[0488]FIG. 17 shows amounts of transmission path variation along a timeaxis. Transmission path variation (I0, Q0) 1701 at time 0 (zero) isfound by correlation calculation. In the same manner, followingcombinations are found at respective times by correlation calculations:

[0489] data symbol 1702 and transmission path variation (I1, Q1) at time1

[0490] data symbol 1703 and transmission path variation (I2, Q2) at time2

[0491] data symbol 1704 and transmission path variation (I3, Q3) at time3

[0492] data symbol 1705 and transmission path variation (I4, Q4) at time4

[0493] data symbol 1706 and transmission path variation (I5, Q5) at time5

[0494] data symbol 1707 and transmission path variation (I6, Q6) at time6.

[0495]FIG. 23 shows a structure of transmission path variationestimation units 506, 518 of channel A and estimation units 508, 520 ofchannel B shown in FIG. 5.

[0496] Pilot symbol correlation calculation unit 2303 receives in-phasecomponent 2301, quadrature-phase component 2302 of a receptionquadrature baseband signal, and pilot-symbol series 2304, then outputsin-phase component 2305, quadrature-phase component 2306 of thereception quadrature baseband signal of the pilot symbols undergone thecorrelation calculations.

[0497] Transmission path variation estimation unit 2307 receivesin-phase component 2305 and quadrature-phase component 2306, and outputstransmission-path variation estimation signal 2308.

[0498] The transmission method in accordance with this fifth embodimentis demonstrated hereinafter with reference to FIGS. 20 and 21.

[0499] The signal point of pilot symbol 2001 of channel A at time 0 isplaced at point 2101 (1, 1) in FIG. 21. The signal point of pilot symbol2002 of channel A at time 1 is placed at point 2101 (1, 1) in FIG. 21.The signal point of pilot symbol 2003 of channel A at time 2 is placedat point 2101 (1, 1) in FIG. 21. The signal point of pilot symbol 2004of channel A at time 3 is placed at point 2102 (1, 1) in FIG. 21.

[0500] The signal point of pilot symbol 2010 of channel B at time 0 isplaced at point 2101 (1, 1) in FIG. 21. The signal point of pilot symbol2011 of channel B at time 1 is placed at point 2101 (1, 1) in FIG. 21.The signal point of pilot symbol 2012 of channel B at time 2 is placedat point 2102 (1, 1) in FIG. 21. The signal point of pilot symbol 2013of channel B at time 3 is placed at point 2102 (1, 1) in FIG. 21.

[0501] In a similar way to what discussed above, the signal point ofpilot symbol 2006 is placed at the same place as that of pilot symbol2001. The signal points of pilot symbols 2007, 2008, 2009 are placed atthe same places of pilot symbols 2002, 2003, 2004 respectively. In thesame manner, the signal points of pilot symbols 2015, 2016, 2017, 2018are placed at the same places of pilot symbols 2010, 2011, 2012, 2013respectively.

[0502] As such, sequential pilot symbols 2001, 2002, 2003, 2004 ofchannel A has correlation of 0 (zero) with sequential pilot symbols2010, 2011, 2012, 2013 of channel B.

[0503] Next, an operation of the transmission apparatus is demonstratedhereinafter with reference to FIG. 2 and FIG. 22.

[0504] In FIG. 2, frame signal generator 209 outputs the information ofthe frame structure shown in FIG. 20 as frame signal 210. Modulationsignal generator 202 of channel A receives frame signal 210 andtransmission digital signal 201 of channel A, then outputs modulationsignal 203 of channel A in accordance with the frame structure.Modulation signal generator 212 of channel B receives frame signal 210and transmission digital signal 211 of channel B, then outputsmodulation signal 213 of channel B in accordance with the framestructure.

[0505] An operation of modulation signal generators 202 and 212 at theprocess discussed above is described using transmitter 220 of channel Aas an example with reference to FIG. 22.

[0506] Data symbol modulation signal generator 2202 receivestransmission digital signal 2201, i.e. transmission digital signal 201of channel A in FIG. 2, and frame signal 2208, i.e. frame signal 210 inFIG. 2. When frame signal 208 indicates a data symbol, generator 2202provides signal 2201 with QPSK modulation, and outputs in-phasecomponent 2203 and quadrature-phase component 2204 of a transmissionquadrature baseband signal of the data symbol.

[0507] Pilot symbol modulation signal generator 2205 receives framesignal 2208. When signal 2208 indicates a pilot symbol, generator 2205outputs in-phase component 2206 and quadrature-phase component 2207 of atransmission quadrature baseband signal of the pilot symbol.

[0508] In-phase component switcher 312 receives the following signals:

[0509] in-phase component 2203 of a data symbol transmission quadraturebaseband signal;

[0510] in-phase component 2206 of a pilot symbol transmission quadraturebaseband signal; and

[0511] frame signal 2208.

[0512] Switcher 312 then selects an in-phase component of thetransmission quadrature baseband signal corresponding to the symbolindicated by frame signal 2208, and outputs the selected one as in-phasecomponent 2210 of the selected transmission quadrature baseband signal.

[0513] Quadrature-phase component switcher 2211 receives the followingsignals:

[0514] quadrature-phase component 2204 of data symbol transmissionquadrature baseband signal;

[0515] quadrature-phase component 2207 of pilot symbol transmissionquadrature baseband signal; and

[0516] frame signal 2208.

[0517] Switcher 2211 then selects a quadrature-phase component of atransmission quadrature baseband signal corresponding to the symbolindicated by frame signal 2208, and outputs the selected one asquadrature-phase component 2212 of the selected transmission orthogonalbase-band.

[0518] Orthogonal modulator 2213 receives in-phase component 2210 andquadrature-phase component 2212 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal2214, i.e. signal 203 shown in FIG. 2.

[0519] Next, an operation of the reception apparatus, in particular,operations of transmission path variation estimation unit 506 of channelA, transmission path variation estimation unit 508 of channel B, andsignal processor 525, with reference to FIG. 5 and FIG. 23. Estimationunit 506 of channel A is taken as an example for the descriptionpurpose.

[0520] Pilot correlation calculation unit 2303 shown in FIG. 23 receivesin-phase component 2301, quadrature-phase component 2302 of a receptionquadrature signal, in which channel A and channel B are mixed with eachother, received by antenna 501, and pilot symbol series 2304 of channelA, then detects pilot symbols in in-phase component 2301 andquadrature-phase component 2302. Calculation unit 2303 then calculatescorrelation between the pilot symbol section detected and pilot-symbolseries 2304, and outputs in-phase component 2305, quadrature-phasecomponent 2306 undergone the correlation calculation.

[0521] The pilot-symbol series of channel A can be formed of thein-phase component and the quadrature-phase component. In such a case,channel B component of the pilot symbol in in-phase component 2301 andquadrature-phase component 2302 of the reception quadrature basebandsignal can be removed by the correlation calculation because the pilotsymbol series of channel A is orthogonal to the pilot symbols series ofchannel B.

[0522] Transmission path variation estimation unit 2307 is describedwith reference to FIG. 17. Distortions (I0, Q0) and (I6, Q6) in FIG. 17are found by pilot-symbol correlation calculation unit 2303. Data-symboltransmission path variations (I1, Q1), (I2, Q2), (I3, Q3), (I4, Q4),(I5, Q5) are found from distortions (I0, Q0) and (I6, Q6), thenestimation unit 2307 outputs those distortions as transmission pathvariation estimation signal 2308.

[0523] In a similar way to estimation unit 506 of channel A,transmission path variation estimation unit 508 of channel B outputstransmission path variation estimation signal 509 of reception signal502 in which channel A and channel B are mixed with each other.Estimation unit 518 of channel A and estimation unit 520 of channel Boutput variation estimation signal 519 of channel A and variationestimation signal 521 of channel B respectively from reception signal514 where channel A and channel B are mixed.

[0524] The foregoing description expresses the transmission pathvariation in (I, Q); however, the distortion can be expressed in powerand phase, so that estimation signals 507, 519 of channel A andestimation signal 509, 521 of channel B can be expressed in power andphase.

[0525] The foregoing structure and operation allow the receptionapparatus to demultiplex the modulation signals of channel A from thoseof channel B, so that the signals can be demodulated.

[0526] In this fifth embodiment, the number of channels to bemultiplexed is two, however, the embodiment is not limited to twochannels, and not limited to the frame structure shown in FIG. 20. Thetransmission path variation can be estimated using the pilot symbol asan example, and other symbols can be used for this purpose as long asthey can estimate the distortion.

[0527] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0528] The structure of the transmission apparatus of this embodiment isnot limited to what is shown in FIG. 2 or FIG. 22, and when the numberof channels increase, the structure formed of elements 201 through 208shown in FIG. 2 is added accordingly.

[0529] The structure of the reception apparatus of this embodiment isnot limited to what is shown in FIG. 5 or FIG. 23, and when the numberof channels increase, the number of channel estimation units increasesaccordingly.

[0530] As discussed above, the fifth exemplary embodiment describes thetransmission method of transmitting modulation signals of a plurality ofchannels from a plurality of antennas to the same frequency band. Moreparticularly, a demodulation symbol to be inserted into a channel isformed of a plurality of sequential symbols, and each one ofdemodulation symbols of respective channels is placed at the same timeand orthogonal to each other. The fifth embodiment also describes thetransmission apparatus and the reception apparatus to be used in theforegoing transmission method. The foregoing transmission method,transmission apparatus and reception apparatus allow multiplexingmodulation signals of a plurality of channels to the same frequencyband. Through this operation, the transmission rate of data can beincreased, at the same time, the demodulation symbol has resistance tonoises, so that an accuracy of channel estimation in the receptionapparatus is increased. As a result, transmission quality of data isimproved.

[0531] Exemplary Embodiment 6

[0532] The sixth exemplary embodiment describes the transmission methodwhich transmits modulation signals of a plurality of channels to thesame frequency band from a plurality of antennas. More particularly, inthis method, at the time when a demodulation symbol is inserted in achannel having a frame structure in accordance with OFDM method and inthe symbols of other channels of sub-carriers, both of the same phasesignal and a quadrature signal in the in-phase-quadrature plane are madeto be zero signals. The sixth embodiment also describes a transmissionapparatus and a reception apparatus to be used in the foregoingtransmission method.

[0533]FIG. 4 shows a placement of signal points in on-phase-quadrature(I-Q) plane. FIG. 24 shows examples of frame structure 2410 of channel Aand frame structure 2420 of channel B along a frequency axis. Framestructure 2410 includes pilot symbol 2401 and data symbol 2402. As shownin FIG. 24, at time 0 of channel A, sub-carrier 2 is assigned as pilotsymbol. At this time, assume that channel B has a symbol of (I, Q)=(0,0). As such, assume that at a certain time and a certain frequency, whenchannel A shows a pilot symbol, channel B has a symbol of (I, Q)=(0, 0).On the contrary, when channel B shows a pilot symbol, channel A has asymbol of (I, Q)=(0, 0).

[0534]FIG. 25 shows a structure of the transmission apparatus inaccordance with the sixth embodiment, and the transmission apparatus isformed of channel A transmitter 2530, channel B transmitter 2540 andframe signal generator 2521.

[0535] Transmitter 2530 of channel A comprises serial-parallel converter2502, inverse discrete Fourier transformer 2504, radio unit 2506, poweramplifier 2508, and antenna 2510.

[0536] Transmitter 2540 of channel B comprises serial-parallel converter2512, inverse discrete Fourier transformer 2514, radio unit 2516, poweramplifier 2518, and antenna 2520.

[0537] Frame signal generator 2521 outputs the information of the framestructure as frame signal 2522.

[0538] Serial-parallel converter 2502 of channel A receives transmissiondigital signal 2501 of channel A and frame signal 2522, and outputsparallel signal 2503 of channel A in accordance with the framestructure.

[0539] Inverse discrete Fourier transformer 2504 of channel A receivesparallel signal 2503, and outputs signal 2505 undergone the inversediscrete Fourier transformation of channel A.

[0540] Radio unit 2506 of channel A receives signal 2505, and outputstransmission signal 2507 of channel A.

[0541] Power amplifier 2508 of channel A receives and amplifiestransmission signal 2507, and outputs transmission signal 2509 asradio-wave from antenna 2510 of channel A.

[0542] Serial-parallel converter 2512 of channel B receives transmissiondigital signal 2511 of channel B and frame signal 2522, and outputsparallel signal 2513 of channel B in accordance with the framestructure.

[0543] Inverse discrete Fourier transformer 2514 of channel B receivesparallel signal 2513, and outputs signal 2515 undergone the inversediscrete Fourier transformation of channel B.

[0544] Radio unit 2516 of channel B receives signal 2515, and outputstransmission signal 2517 of channel B.

[0545] Power amplifier 2518 of channel B receives and amplifiestransmission signal 2517, and outputs transmission signal 2519 asradio-wave from antenna 2520 of channel B.

[0546]FIG. 26 shows a structure of the reception apparatus in accordancewith this embodiment, and radio unit 2603 receives signal 2602 receivedby antenna 2601, then outputs a reception quadrature baseband signal2604.

[0547] Fourier transformer 2605 receives quadrature baseband signal2604, and outputs parallel signal 2606.

[0548] Transmission path variation estimation unit 2607 of channel Areceives parallel signal 2606, and outputs transmission path variationparallel signal 2608 of channel A.

[0549] Transmission path variation estimation unit 2609 of channel Breceives parallel signal 2606, and outputs transmission path variationparallel signal 2610 of channel B.

[0550] Radio unit 2613 receives signal 2612 received by antenna 2611,and outputs reception quadrature baseband signal 2614.

[0551] Fourier transformer 2615 receives signal 2614, and outputsparallel signal 2616.

[0552] Transmission path variation estimation unit 2617 of channel Areceives parallel signal 2616, and outputs transmission path variationparallel signal 2618 of channel A.

[0553] Transmission path variation estimation unit 2619 of channel Breceives parallel signal 2616, and outputs transmission path variationparallel signal 2620 of channel B.

[0554] Signal processor 2621 receives parallel signals 2606, 2616,transmission path variation parallel signals 2608, 2618 of channel A,and transmission path variation parallel signals 2610, 2620 of channelB, then demultiplexes the signals of channel A from those of channel B,and outputs parallel signal 2622 of channel A as well as parallel signal2623 of channel B.

[0555] Demodulator 2624 of channel A receives parallel signal 2622 ofchannel A, and outputs reception digital signal 2625 of channel A.

[0556] Demodulator 2626 of channel B receives parallel signal 2623 ofchannel B, and outputs reception digital signal 2627 of channel B.

[0557]FIG. 27 shows a transmission path variation of a carrier along atime axis. Specifically, relations between frame structure 2720 ofcarrier 1 of channel A, transmission path variation 2721 of carrier 1 ofchannel A, frame structure 2730 of carrier 1 of channel B, transmissionpath variation 2731 of carrier 1 of channel B, and reception base-bandsignal 2732 of carrier 1.

[0558] Frame structure 2720 includes symbol 2701 of a carrier of channelA at time 0, symbol 2702 of a carrier of channel A at time 1, symbol2703 of a carrier of channel A at time 2, symbol 2704 of a carrier ofchannel A at time 3, symbol 2705 of a carrier of channel A at time 4,symbol 2706 of a carrier of channel A at time 5. Frame structure 2730includes symbol 2707 of a carrier of channel B at time 0, symbol 2708 ofa carrier of channel B at time 1, symbol 2709 of a carrier of channel Bat time 2, symbol 2710 of a carrier of channel B at time 3, symbol 2711of a carrier of channel B at time 4, symbol 2712 of a carrier of channelB at time 5.

[0559]FIG. 28 shows a structure of transmission path variationestimation units and a signal processor of carrier 1.

[0560] Estimation unit 2803 of carrier 1 of channel A receives in-phasecomponent 2801 and quadrature-phase component 2802 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2804 of carrier 1 of channel A.

[0561] Estimation unit 2805 of carrier 1 of channel B receives in-phasecomponent 2801 and quadrature-phase component 2802 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2806 of carrier 1 of channel B.

[0562] Estimation unit 2809 of carrier 1 of channel A receives in-phasecomponent 2807 and quadrature-phase component 2808 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2810 of carrier 1 of channel A.

[0563] Estimation unit 2811 of carrier 1 of channel B receives in-phasecomponent 2807 and quadrature-phase component 2808 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2812 of carrier 1 of channel B.

[0564] Signal processor 2813 of carrier 1 receives the followingsignals:

[0565] in-phase component 2801 and quadrature-phase component 2802 ofcarrier 1 of the parallel signal;

[0566] transmission path variation estimation signal 2804 of carrier 1of channel A;

[0567] transmission path variation estimation signal 2806 of carrier 1of channel B;

[0568] in-phase component 2807 and quadrature-phase component 2808 ofcarrier 1 of the parallel signal;

[0569] transmission path variation estimation signal 2810 of carrier 1of channel A;and

[0570] transmission path variation estimation signal 2812 of carrier 1of channel B.

[0571] Signal processor 2813 then demultiplexes the signals of channel Afrom channel B, and outputs in-phase component 2814, quadrature-phasecomponent 2815 of carrier 1 of the parallel signal of channel A, andin-phase component 2816, quadrature-phase component 2817 of carrier 1 ofthe parallel signal of channel B.

[0572] An operation of the transmission apparatus is demonstratedhereinafter with reference to FIGS. 4, 24 and 25. In FIG. 24, the signalpoint of pilot symbol 2401 corresponds to signal point 402 shown in FIG.4. The signal point of symbol of (I, Q)=(0, 0) corresponds to signalpoint 403 shown in FIG. 4.

[0573] In FIG. 25, frame signal generator 2521 outputs the informationabout the frame structure shown in FIG. 24 as frame signal 2522.Serial-parallel converter 2502 of channel A receives transmissiondigital signal 2501 of channel A, frame signal 2522, then outputsparallel signal 2503 of channel A in accordance with the frame structureshown in FIG. 24. In a similar way to converter 2502, serial-parallelconverter 2512 of channel B receives transmission digital signal 2511 ofchannel B, frame signal 2522, then outputs parallel signal 2513 ofchannel B in accordance with the frame structure shown in FIG. 24.

[0574] Next, an operation of the reception apparatus is demonstrated, inparticular, operations of transmission path variation estimation units2607, 2617 of channel A, estimation units 2609, 2619 of channel B, andsignal processor 2621 are demonstrated with reference to FIGS. 26, 27and 28 using carrier 1 shown in FIG. 24 as an example.

[0575]FIG. 28 shows a structure where only the functions of carrier 1are extracted from estimation units 2607, 2617 of channel A, estimationunits 2609, 2619 of channel B, and signal processor 2621 shown in FIG.26.

[0576] In FIG. 28, in-phase component 2801 and quadrature-phasecomponent 2802 of carrier 1 of the parallel signal correspond to thecomponent of carrier 1 of parallel signal 2606 shown in FIG. 26. Astructure of transmission path variation estimation unit 2803 of carrier1 of channel A shows the function of carrier 1 in estimation unit 2607shown in FIG. 26. Estimation signal 2804 of channel A is a component ofcarrier 1 of parallel signal 2608 shown in FIG. 26. A structure oftransmission path variation estimation unit 2805 of carrier 1 of channelB shows the function of carrier 1 in estimation unit 2609 shown in FIG.26. Estimation signal 2806 of channel B is a component of carrier 1 ofparallel signal 2610 shown in FIG. 26.

[0577] In-phase component 2807 and quadrature-phase component 2808 ofcarrier 1 of the parallel signal correspond to the component of carrier1 of parallel signal 2616 shown in FIG. 26. A structure of transmissionpath variation estimation unit 2809 of carrier 1 of channel A shows thefunction of carrier 1 in estimation unit 2617 shown in FIG. 26.Estimation signal 2810 of channel A is a component of carrier 1 ofparallel signal 2618 in FIG. 26. A structure of transmission pathvariation estimation unit 2811 of carrier 1 of channel B shows thefunction of carrier 1 in estimation unit 2619 shown in FIG. 26.Estimation signal 2812 of channel B is a component of carrier 1 ofparallel signal 2620 in FIG. 26.

[0578] Signal processor 2813 of carrier 1 shows the function of carrier1 in signal processor 2621. In-phase component 2814 and quadrature-phasecomponent 2815 of carrier 1 of the parallel signal of channel Acorrespond to the component of carrier 1 of parallel signal 2622 ofchannel A shown in FIG. 26. In-phase component 2816 and quadrature-phasecomponent 2817 of carrier 1 of the parallel signal of channel Bcorrespond to the component of carrier 1 of parallel signal 2623 ofchannel B shown in FIG. 26.

[0579] Next, operations of transmission path variation estimation units2803, 2809 of carrier 1 of channel A, and estimation units 2805, 2811 ofcarrier 1 of channel B shown in FIG. 28 are demonstrated using units2803 and 2805 as examples.

[0580] In FIG. 27, assume that a reception base-band signal of carrier 1at time 0 through time 5, i.e. in-phase component 2807 andquadrature-phase component 2808 of carrier 1 in the parallel signal, are(I0, Q0), (I1, Q1), (I2, Q2), (I3, Q3), (I4, Q4), and (I5, Q5).

[0581] Assume that the transmission path variation of carrier 1 ofchannel A at time 0 through time 5, i.e. transmission variationestimation signal 2804 of carrier 1 of channel A, are (Ia0, Qa0), (Ia1,Qa1), (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), and (Ia5, Qa5).

[0582] Assume that the transmission path variation of channel B ofcarrier 1 at time 0 through time 5, i.e. transmission variationestimation signal 2806 of channel B of carrier 1, are (Ib0, Qb0), (Ib1,Qb1), (Ib2, Qb2), (Ib3, Qb3), (Ib4, Qb4), and (Ib5, Qb5).

[0583] In the foregoing case, since (I0, Q0) has only a pilot componentof channel B of carrier 1, (Ib0, Qb0)=(I0, Q0). Similarly, since II1,Q1) has only a pilot component of channel A of carrier 1, (Ia1,Qa1)=(II1, Q1). For instance, (Ia0, Qa0)=(Ia1, Qa1)=(Ia2, Qa2)=(Ia3,Qa3)=(Ia4, Qa4)=(Ia5, Qa5), and (Ib0, Qb0)=(Ib1, Qb1)=(Ib2, Qb2)=(Ib3,Qb3)=(Ib4, Qb4)=(Ib5, Qb5) will find transmission path variationestimation signals 2804 and 2806 of channels A and B respectively ofcarrier 1.

[0584] A similar operation to what is discussed above will findtransmission path variation estimation signals 2810 and 2812 of channelsA and B respectively of carrier 1.

[0585] Signal processor 2813 of carrier 1 receives the followingsignals:

[0586] variation estimation signals 2804, 2810 of channel A;

[0587] variation estimation signals 2806, 2812 of channel B;

[0588] in-phase component 2801, quadrature-phase component 2802 of theparallel signal; and

[0589] in-phase component 2807, quadrature-phase component 2808 of theparallel signal.

[0590] Then processor 2813 carries out matrix calculations fordemultiplexing the signals of channel A from channel B, and outputs thefollowing signals:

[0591] in-phase component 2814 and quadrature-phase component 2815 ofcarrier 1 of the parallel signal of channel A; and

[0592] in-phase component 2816 and quadrature-phase component 2817 ofcarrier 1 of the parallel signal of channel B.

[0593] As a result, modulation signals of channel A and channel B can bedemultiplexed from each other, and the modulation signals can bedemodulated.

[0594] The foregoing description expresses the transmission pathvariation in (I, Q); however, the distortion can be expressed in powerand phase, so that estimation signals 2804, 2810 of channel A andestimation signal 2806, 2812 of channel B can be expressed in power andphase.

[0595] Signals of channel A and channel B of carriers 2, 3, and 4 can bedemultiplexed from each other in a similar way to what is discussedabove using the structure shown in FIG. 28.

[0596] A method of estimating a transmission path of carrier 2 isdemonstrated hereinafter. The reception apparatus of this embodiment canestimate a fluctuation of the transmission path from a pilot symbol ofcarrier 2 at time 0 shown in FIG. 24. Also the reception apparatus canestimate the fluctuation of the transmission path of carrier 2 at time 1from the pilot symbols of carrier 1 and carrier 3 at time 1. As such,the transmission path fluctuation of carrier 2 can be estimated by anestimated value of the transmission path fluctuation of carrier 2estimated at time 0 and time 1. As a result, the transmission pathfluctuation can be estimated with accuracy.

[0597] A method of estimating a transmission path of, e.g. carrier 2shown in FIG. 24, is demonstrated hereinafter. The reception apparatuscan estimate a fluctuation of the transmission path from a pilot symbolof carrier 2 at time 0 shown in FIG. 24. Also the reception apparatuscan estimate the fluctuation of the transmission path of carrier 2 attime 1 from the pilot symbols of carrier 1 and carrier 3 at time 1. Assuch, the transmission path fluctuation of carrier 2 can be estimated byan estimated value of the transmission path fluctuation of carrier 2estimated at time 0 and time 1. As a result, the transmission pathfluctuation can be estimated with accuracy.

[0598] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0599] In this embodiment, an accuracy of demultiplexing the modulationsignals between channel A and channel B at the reception apparatusdepends on a quality of the pilot symbol received. Thus strongerresistance of the pilot symbol to noise increases the accuracy ofisolation between the modulation signals of channel A and channel B. Asa result, the quality of data received can be improved. The way how toachieve this goal is described hereinafter.

[0600] In FIG. 4, assume that the pilot symbol has amplitude Ap from theorigin, and QPSK has the greatest signal-point amplitude Aq from theorigin. In this status, the relation of Ap>Aq increases the resistanceto noise of the pilot symbol, so that the accuracy of demultiplexing themodulation signals of channel A from those of channel B. As a result,the quality of data received can be improved.

[0601] In this embodiment, the number of channels to be multiplexed aretwo; however, other numbers can be applicable to the embodiment. Theframe structure is not limited to what is shown in FIG. 24. The pilotsymbol is taken as an example for demultiplexing the channels; however,other symbols as long as they are used for demodulation can be alsoapplicable. A modulation method of the data symbol is not limited toQPSK modulation, but respective channels can undergo differentmodulations.

[0602] The structure of the transmission apparatus of this embodiment isnot limited to what is shown in FIG. 25, and when the number of channelsincrease, the structure formed of elements 2501 through 2510 shown inFIG. 25 is added accordingly.

[0603] The structure of the reception apparatus of this embodiment isnot limited to what is shown in FIGS. 26, 28, and when the number ofchannels increase, the number of channel estimation units increasesaccordingly.

[0604] As discussed above, the sixth exemplary embodiment describes thetransmission method which transmits modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas. Moreparticularly, in this method, at the time when a demodulation symbol isinserted in a channel having a frame structure in accordance with OFDMmethod and in the symbols of other channels of sub-carriers, both of thesame phase signal and a quadrature signal in the in-phase-quadratureplane are made to be zero signals. The sixth embodiment also describesthe transmission apparatus and the reception apparatus to be used in theforegoing transmission method. The foregoing method and structure allowincreasing the data transmission rate, and at the same time, thereception apparatus can demultiplex the multiplexed modulation signalswith ease.

[0605] Exemplary Embodiment 7

[0606] The seventh exemplary embodiment describes a transmission methodthat switches between a method of transmitting modulation signals of aplurality of channels to the same frequency band from a plurality ofantennas and a method of transmitting a modulation signal of one channelfrom an antenna. The embodiment also describes a transmission apparatusand a reception apparatus to be used in the foregoing transmissionmethod.

[0607]FIG. 29 shows a frame structure in accordance with the seventhembodiment, specifically, frame structure 2910 of channel A and framestructure 2920 of channel B. Frame structure 2910 includes multiplexinformation symbols 2901, 2903, and frame symbol groups 2902, 2904 offrame A. Structure 2920 includes frame symbol group 2905 of channel B.

[0608] In this case, multiplex information symbol 2901 includes theinformation that indicates that the frame symbol groups of channel A andchannel B are transmitted simultaneously. Symbol group 2902 of channel Aand symbol group 2905 of channel B are thus transmitted simultaneously.

[0609] Multiplex information symbol 2903 includes the information whichindicates that only the frame symbol group of channel A is transmitted,so that only frame symbol group 2904 of channel A is transmitted.

[0610]FIG. 30 shows a frame structure in accordance with the seventhembodiment, specifically, frame structure 3010 of channel A and framestructure 3020 of channel B. Structure 3010 includes multiplexinformation symbol 3001 and information symbol 3002.

[0611] In this case, the multiplex information symbol at time 0 includesthe information which indicates that the information symbol of channel Aand that of channel B are transmitted simultaneously at time 1 throughtime 5. Those symbols are thus transmitted simultaneously at time 1through time 5.

[0612] The multiplex information symbol at time 6 includes theinformation which indicates that only the information of channel A istransmitted at time 7 through time 11.

[0613]FIG. 31 shows a structure of, e.g. a transmission apparatus at abase station, and the apparatus comprises channel A transmitter 3120,channel B transmitter 3130, and frame signal generator 3118. Transmitter3120 comprises modulation signal generator 3102, radio unit 3105, poweramplifier 3107, and antenna 3109. Transmitter 3130 comprises modulationsignal generator 3102, radio unit 3111, power amplifier 3113, andantenna 3115.

[0614] Modulation signal generator 3102 receives transmission digitalsignal 3101, frame signal 3119, and outputs modulation signal 3103 ofchannel A and modulation signal 3110 of channel B in accordance with theframe structure.

[0615] Radio unit 3105 of channel A receives modulation signal 3103 ofchannel A, and outputs transmission signal 3106 of channel A.

[0616] Power amplifier 3107 of channel A receives transmission signal3106 of channel A, then amplifies it, and outputs amplified transmissionsignal 3108 from antenna 3109 as radio wave.

[0617] Radio unit 3111 of channel B receives modulation signal 3110 ofchannel B, and outputs transmission signal 3112 of channel B.

[0618] Power amplifier 3113 of channel B receives transmission signal3112 of channel B, then amplifies it, and outputs amplified transmissionsignal 3114 from antenna 3115 as radio wave.

[0619] Frame signal generator 3118 receives radio-wave propagationenvironmental information 3116, transmission data amount information3117, then outputs frame signal 3119.

[0620]FIG. 32 shows a structure of, e.g. a reception apparatus at aterminal in accordance with this embodiment. Radio unit 3203 receivessignal 3202 received by antenna 3201, and outputs reception quadraturebaseband signal 3204.

[0621] Multiplex information symbol demodulator 3205 receives base-bandsignal 3204, and multiplex information data 3206.

[0622] Transmission path variation estimation unit 3207 of channel Areceives base-band signal 3204, and outputs variation estimation signal3208. Transmission path variation estimation unit 3209 of channel Breceives base-band signal 3204, and outputs variation estimation signal3210.

[0623] Radio unit 3213 receives signal 3212 received by antenna 3211,and outputs reception quadrature baseband signal 3214. Transmission pathvariation estimation unit 3215 of channel A receives base-band signal3214, and outputs variation estimation signal 3216. Transmission pathvariation estimation unit 3209 of channel B receives base-band signal3214, and outputs variation estimation signal 3218.

[0624] Signal processor 3219 receives the following signals:

[0625] transmission path variation estimation signals 3208, 3216 ofchannel A;

[0626] transmission path variation estimation signals 3210, 3218 ofchannel B;

[0627] reception quadrature baseband signals 3204, 3214; and

[0628] multiplex information data 3206.

[0629] Signal processor 3219 then outputs signal 3220 of channel A andsignal 3221 of channel B based on multiplex information data 3206.

[0630] Demodulator 3222 receives signals 3220, 3221, data 3206, andbased on data 3206, outputs reception digital signal 3223.

[0631] Radio-wave propagation environment estimation unit 3224 receivesbase-band signal 3204, 3214, then estimates the radio-wave propagationenvironment, e.g. a received signal strength intensity or a spatialcorrelation of the radio-wave propagation environment, and outputsradio-wave propagation environment estimation signal 3225.

[0632] The transmission apparatus of, e.g. a base station, in accordancewith the embodiment with reference to FIGS. 29, 31 and 32.

[0633] The reception apparatus shown in FIG. 32 includes radio-wavepropagation environment estimation unit 3224 which receives receptionquadrature baseband signal 3204, 3214. Estimation unit 3224 thenestimates the radio-wave propagation environment, e.g. a received signalstrength intensity or a spatial correlation of the radio-wavepropagation environment, and outputs radio wave propagation environmentestimation signal 3225. The information of signal 3225 is transmitted asdata from a transmitter of the terminal, and the base station receivesand demodulates it for obtaining the information corresponding to signal3225. This information corresponds to radio-wave propagationenvironmental information 3116 shown in FIG. 31.

[0634] Frame signal generator 3118 receives information 3116,transmission data amount information 3117, and outputs frame signal 3119that includes, e.g. the following information as shown in FIG. 29:

[0635] Multiplex information symbol 2901 indicates that the frame symbolgroups of channels A and B are simultaneously transmitted;

[0636] Frame symbol group 2902 of channel A and frame symbol group 2905of channel B indicate that both of them are transmitted simultaneously;

[0637] Multiplex information symbol 2903 of channel A indicates thatonly the frame symbol groups of channel A are transmitted; and

[0638] Multiplex information symbol 2904 of channel A indicates thatonly the frame symbol groups of channel A are transmitted.

[0639] Modulation signal generator 3102 shown in FIG. 31 receivestransmission digital signal 3101, frame signal 3119, and outputsmodulation signal 3103 of channel A and modulation signal 3110 ofchannel B.

[0640] The reception apparatus of the terminal in accordance with theseventh embodiment is described with reference to FIG. 29 and FIG. 32.Multiplex information symbol decoder 3205 receives reception quadraturebaseband signal 3204, then demodulates the multiplex information symbolshown in FIG. 29. When decoder 3205 decodes, e.g. multiplex informationsymbol 2901, decoder 3205 outputs the following information as multiplexinformation data 3206: the information indicating that the frame symbolgroups of channels A and B are transmitted simultaneously. When decoder3205 decodes, e.g. multiplex information symbol 2903, decoder 3205outputs the following information as multiplex information data 3206:the information indicating that the frame symbol group of only channel Ais transmitted.

[0641] Signal processor 3219 receives the following signals:

[0642] transmission path variation estimation signals 3208, 3216 ofchannel A;

[0643] transmission path variation estimation signals 3210, 3218 ofchannel B;

[0644] reception quadrature baseband signals 3204, 3214; and

[0645] multiplex information data 3206.

[0646] When data 3206 indicates that the frame symbol groups of channelsA and B are transmitted simultaneously, processor 3219 carries outinverse matrix calculations from estimation signals 3208, 3216 ofchannel A, estimation signals 3210, 3218 of channel B, base-band signals3204, 3214. Then processor 3219 demultiplexes the signals of channel Afrom those of channel B, and outputs signal 3220 of channel A and signal3221 of channel B. When multiplex information data 3206 indicates thatthe frame symbol group of only channel A is transmitted, processor 3219outputs only signal 3220 of channel A.

[0647] Demodulator 3222 receives signal 3220 of channel A, signal 32210of channel B, and multiplex information data 3206. When data 3206indicates that the frame symbol groups of channels A and B aresimultaneously transmitted, decoder 3222 decodes signals 3220, 3221.When data 3206 indicates that the frame symbol group of only channel Ais transmitted, demodulator 3222 demodulates signal 3220 of channel A.Then demodulator 3222 outputs reception digital signal 3223.

[0648] In the case of orthogonal frequency multiplexing (OFDM) system, asimilar way to what is discussed above is applicable. The transmitter ofthe base station, for instance, in accordance with the seventhembodiment is demonstrated hereinafter with reference to FIGS. 30, 31,32.

[0649] The reception apparatus shown in FIG. 32 includes radio-wavepropagation environment estimation unit 3224 which receives receptionquadrature baseband signal 3204, 3214. Estimation unit 3224 thenestimates the radio-wave propagation environment, e.g. received signalstrength intensity or spatial correlation of the radio-wave propagationenvironment, and outputs radio wave propagation environment estimationsignal 3225. The information of signal 3225 is transmitted as data froma transmitter of the terminal, and the base station receives anddemodulates it for obtaining the information corresponding to signal3225. This information corresponds to radio-wave propagationenvironmental information 3116 shown in FIG. 31.

[0650] Frame signal generator 3118 receives information 3116,transmission data amount information 3117, and outputs frame signal 3119that includes, e.g. the following information as shown in FIG. 30:

[0651] multiplex information symbol at time 0 indicating that theinformation symbols of channels A and B are simultaneously transmittedat time 1-time 5, and showing the frame structure where both ofinformation symbols of channel A and channel B are transmittedsimultaneously at time 1-time 5;

[0652] multiplex information symbol at time 6 indicating that only theinformation of channel A is transmitted at time 7-time 11, and showingthe frame structure where the information of only channel A istransmitted at time 7-time 11.

[0653] Generator 3118 outputs the foregoing information as frame signal3119. Modulation signal generator 3102 receives transmission digitalsignal 3101, frame signal 3119, and outputs modulation signal 3103 ofchannel A and modulation signal 3110 of channel B in accordance with theframe structure.

[0654] Next, a reception apparatus of a terminal in accordance with theseventh embodiment is described with reference to FIG. 30 and FIG. 32.

[0655] Multiplex information symbol demodulator 3205 receives base-bandsignal 3204, and demodulates the multiplex information symbol shown inFIG. 30. When, for instance, demodulator 3205 demodulates the multiplexinformation symbol at time 0, demodulator 3205 outputs the informationindicating that the frame symbol groups of channels A and B aretransmitted simultaneously. When demodulator 3205 demodulates the symbolat time 6, demodulator 3205 outputs the information indicating that theframe symbol group of only channel A is transmitted. As such, theinformation of either one of the foregoing cases is output as multiplexinformation data 3206.

[0656] Signal processor 3219 receives the following signals:

[0657] transmission path variation estimation signals 3208, 3216 ofchannel A;

[0658] transmission path variation estimation signals 3210, 3218 ofchannel B;

[0659] reception quadrature baseband signals 3204, 3214; and

[0660] multiplex information data 3206.

[0661] When data 3206 indicates that the frame symbol groups of channelsA and B are transmitted simultaneously, processor 3219 carries outinverse matrix calculations from estimation signals 3208, 3216 ofchannel A, estimation signals 3210, 3218 of channel B, base-band signals3204, 3214. Then processor 3219 demultiplexes the signals of channel Afrom those of channel B, and outputs signal 3220 of channel A and signal3221 of channel B. When multiplex information data 3206 indicates thatthe frame symbol group of only channel A is transmitted, processor 3219outputs only signal 3220 of channel A.

[0662] Demodulator 3222 receives signal 3220 of channel A, signal 32210of channel B, and multiplex information data 3206. When data 3206indicates that the frame symbol groups of channels A and B aresimultaneously transmitted, decoder 3222 decodes signals 3220, 3221.When data 3206 indicates that the frame symbol group of only channel Ais transmitted, demodulator 3222 demodulates signal 3220 of channel A.Then demodulator 3222 outputs reception digital signal 3223.

[0663] In this embodiment, the number of channels to be multiplexed aretwo; however, other numbers can be applicable to this embodiment. Theframe structure is not limited to what is shown in FIG. 29 or FIG. 30.

[0664] The structure of the transmission apparatus of this embodiment isnot limited to what is shown in FIG. 31, and when the number of channelsincrease, the structure formed of elements 3103 through 3109 shown inFIG. 31 is added accordingly. The structure of the reception apparatusof this embodiment is not limited to what is shown in FIG. 32.

[0665] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0666] The seventh exemplary embodiment as discussed above describes thetransmission method that switches between the method of transmittingmodulation signals of a plurality of channels to the same frequency bandfrom a plurality of antennas and the method of transmitting a modulationsignal of one channel from an antenna. The embodiment also describes thetransmission apparatus and the reception apparatus used in the foregoingtransmission method. Multiplexing the transmission signals of aplurality of channels to the same frequency band allows the method andthe apparatuses to increase the data transmission rate, and allows thereception apparatus to demultiplex the multiplexed modulation signalsreceived with ease.

[0667] Exemplary Embodiment 8

[0668] The eighth exemplary embodiment describes a transmission methodof multiplexing modulation signals of a plurality of channels to thesame frequency band, more particularly, a method of transmitting asynchronous symbol for the foregoing transmission method. Thisembodiment also describes a transmission apparatus as well as areception apparatus to be used in the foregoing transmission method.

[0669]FIG. 2 shows a structure of the transmission apparatus inaccordance with the eighth embodiment.

[0670]FIG. 4 shows a placement of signal points in thein-phase-quadrature plane in accordance with this embodiment.

[0671]FIG. 33 shows a frame structure along a time-axis in accordancewith this embodiment, and to be more specific, it shows frame structure3310 of channel A and frame structure 3320 of channel B. Framestructures 3310, 3320 include synchronous symbols 3301, 3305, guardsymbols 3302, 3304, and data symbols 3303, 3306.

[0672]FIG. 34 shows a frame structure along a time axis in accordancewith this embodiment, specifically, frame structure 3410 of channel Aand frame structure 3420 of channel B. Structures 3410, 3420 includesynchronous symbols 3401, data symbols 3402, 3404, and guard symbol3403.

[0673]FIG. 35 shows a structure of modulation signal generators 202,212, and the elements operating in a similar way to those in FIG. 3 havethe same reference marks. Synchronous symbol modulation signal generator3501 receives frame signal 311, and outputs in-phase component 3502 andquadrature-phase component 3503 of the transmission quadrature basebandsignal of the synchronous symbol when frame signal 311 indicates thesynchronous symbol.

[0674] In-phase component switcher 312 receives the following signals:

[0675] in-phase component 303 of a data symbol transmission quadraturebaseband signal;

[0676] in-phase component 3502 of the synchronous symbol transmissionquadrature baseband signal;

[0677] in-phase component 309 of a guard symbol transmission quadraturebaseband signal, and frame signal 311,

[0678] then switcher 312 selects the in-phase component of transmissionquadrature baseband signal corresponding to a symbol indicated by framesignal 311, and outputs the selected one as in-phase component 313 ofthe selected transmission quadrature baseband signal.

[0679] Quadrature-phase component switcher 314 receives the followingsignals:

[0680] quadrature-phase component 304 of a data symbol transmissionquadrature baseband signal;

[0681] quadrature-phase component 3503 of the synchronous symboltransmission quadrature baseband signal;

[0682] quadrature-phase component 310 of a guard symbol transmissionquadrature baseband signal, and frame signal 311,

[0683] then selects a quadrature-phase component of a transmissionquadrature baseband signal corresponding to a symbol indicated by framesignal 311, and outputs the selected one as quadrature-phase component315 of the selected transmission quadrature baseband signal.

[0684]FIG. 36 shows a structure of modulation signal generators 202, 212shown in FIG. 2. Guard symbol or synchronous symbol transmission signalgenerator 3601 receives frame signal 311, and outputs in-phase component3602, quadrature-phase component 3603 of the transmission quadraturebaseband signal of the guard symbol or the synchronous symbol.

[0685]FIG. 37 shows a structure of the reception apparatus in accordancewith the eighth embodiment, and its radio unit 3703 receives signal 3702received by antenna 3701, then outputs reception quadrature basebandsignal 3704.

[0686] Transmission path variation estimation unit 3705 receivesbase-band signal 3704 and timing signal 3719, then outputs transmissionpath variation estimation signal 3706.

[0687] Radio unit 3708 receives signal 3707 received by antenna 3706,then outputs reception quadrature baseband signal 3709.

[0688] Transmission path variation estimation unit 3710 receivesbase-band signal 3709 and timing signal 3719, then outputs transmissionpath variation estimation signal 3711.

[0689] Radio unit 3714 receives signal 3713 received by antenna 3712,then outputs reception quadrature baseband signal 3715.

[0690] Transmission path variation estimation unit 3716 receivesbase-band signal 3715 and timing signal 3719, then outputs transmissionpath variation estimation signal 3717.

[0691] Synchronizing unit 3717 receives base-band signal 3715, andsearches for a synchronous symbol transmitted by the transmissionapparatus to synchronize with the transmission apparatus, then outputstiming signal 3719.

[0692] Signal isolator 3720 receives the following signals:

[0693] reception quadrature baseband signals 3704, 3709, 3715;

[0694] transmission path variation estimation signals 3706, 3711, 3717;and

[0695] timing signal 3719.

[0696] Signal isolator 3720 then outputs reception quadrature basebandsignal 3721 of channel A and quadrature baseband signal 3722 of channelB.

[0697] Demodulator 3723 receives signal 3721 of channel A, and outputsreception digital signal 3724. Demodulator 3725 receives signal 3722 ofchannel B, and outputs reception digital signal 3725.

[0698]FIG. 38 shows a structure of the reception apparatus in accordancewith the eighth embodiment, and the elements operating in a similar wayto those in FIG. 37 have the same reference marks.

[0699] Synchronizing unit 3801 receives reception quadrature basebandsignal 3801, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 3802.

[0700] Transmission path variation estimation unit 3705 receivesbase-band signal 3704 and timing signal 3802, then outputs transmissionpath variation estimation signal 3705.

[0701] Synchronizing unit 3803 receives reception quadrature basebandsignal 3809, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 3804.

[0702] Transmission path variation estimation unit 3710 receivesreception quadrature baseband signal 3709 and timing signal 3804, thenoutputs transmission path variation estimation signal 3711.

[0703] Synchronizing unit 3805 receives reception quadrature basebandsignal 3815, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 3806.

[0704] Transmission path variation estimation unit 3716 receivesreception quadrature baseband signal 3715 and timing signal 3806, thenoutputs transmission path variation estimation signal 3717.

[0705]FIG. 39 shows a structure of the reception apparatus in accordancewith the eighth embodiment, and the elements operating in a similar wayto those in FIG. 37 have the same reference marks.

[0706] Received signal strength intensity estimation unit 3901 receivessignal 3702, then estimates the received signal strength intensity, andoutputs received signal strength intensity estimation signal 3902.

[0707] Received signal strength intensity estimation unit 3903 receivessignal 3707, then estimates the received signal strength intensity, andoutputs received signal strength intensity estimation signal 3904.

[0708]FIG. 40 shows a structure of the reception apparatus in accordancewith the eighth embodiment, and the elements operating in a similar wayto those in FIG. 37 or FIG. 39 have the same reference marks.

[0709] Signal selection unit 4001 receives the following signals:

[0710] received signal strength intensity estimation signals 3902, 3904,3906; and

[0711] reception quadrature baseband signal 3704, 3709, 3715,

[0712] then unit 4001 selects, e.g. the reception quadrature basebandsignal supplied from the antenna that receives the signal having thebest electric field among the received signal strength intensityestimation signals, and outputs it as reception quadrature basebandsignal 4002.

[0713] Synchronizing unit 4003 receives reception quadrature basebandsignal 4002 selected, and searches for a synchronous symbol transmittedby the transmission apparatus to synchronize with the transmissionapparatus, then outputs timing signal 4004.

[0714]FIG. 41 shows a structure of the reception apparatus in accordancewith the eighth embodiment, and the elements operating in a similar wayto those in FIG. 39 or FIG. 40 have the same reference marks.

[0715] An operation of the transmission apparatus is demonstratedhereinafter with reference to FIGS. 2, 4, 33, 34, 35 and 36.

[0716] Frame signal generator 209 outputs the information of the framestructure shown in FIG. 33 or FIG. 34 as frame signal 210. Modulationsignal generator 202 of channel A receives frame signal 210 andtransmission digital signal 201 of channel A, then outputs modulationsignal 203 of channel A in accordance with the frame structure.Modulation signal generator 212 of channel B receives frame signal 210and transmission digital signal 211 of channel B, then outputsmodulation signal 213 of channel B in accordance with the framestructure.

[0717] Next, an operation of modulation signal generators 202 and 212 inaccordance with the frame structure shown in FIG. 33 is described withreference to FIG. 35 using a transmitter of channel A as an example.

[0718] Data symbol modulation signal generator 302 receives transmissiondigital signal 301, i.e. transmission digital signal 201 of channel A inFIG. 2, and frame signal 311, i.e. frame signal 210 in FIG. 2. Whenframe signal 311 indicates a data symbol, generator 302 outputs in-phasecomponent 303 and quadrature-phase component 304 of a transmissionquadrature baseband signal of the data symbol.

[0719] Synchronous symbol modulation signal generator 3501 receivesframe signal 311. When frame signal 311 indicates the synchronoussymbol, generator 3501 outputs in-phase component 3502 andquadrature-phase component 3503 of the transmission quadrature basebandsignal of the synchronous symbol.

[0720] Guard symbol modulation signal generator 308 receives framesignal 311. When signal 311 indicates a guard symbol, generator 308outputs in-phase component 309 and quadrature-phase component 310 of atransmission quadrature baseband signal of the guard symbol.

[0721]FIG. 4 shows the signal-point placement of the respective symbolsin an in-phase-quadrature plane of the foregoing operation. Points 401in FIG. 4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 402 indicate the signal-points ofin-phase component 3502 and quadrature-phase component 3503 of thetransmission quadrature baseband signal of the synchronous symbol. Point403 indicates the signal-points of in-phase component 309 andquadrature-phase component 310 of the transmission quadrature basebandsignal of the guard symbol.

[0722] In-phase component switcher 312 receives the following signals:

[0723] in-phase component 303 of data symbol transmission quadraturebaseband signal;

[0724] in-phase component 3502 of synchronous symbol transmissionquadrature baseband signal;

[0725] in-phase component 309 of guard symbol transmission quadraturebaseband signal; and

[0726] frame signal 311.

[0727] Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe signal 311, and outputs the selected one as in-phase component 313of the selected transmission quadrature baseband signal.

[0728] Quadrature-phase component switcher 314 receives the followingsignals:

[0729] quadrature-phase component 304 of data symbol transmissionquadrature baseband signal;

[0730] quadrature-phase component 3503 of synchronous symboltransmission quadrature baseband signal;

[0731] quadrature-phase component 310 of guard symbol transmissionquadrature baseband signal; and

[0732] frame signal 311.

[0733] Switcher 314 then selects a quadrature-phase component of atransmission quadrature baseband signal corresponding to the symbolindicated by frame signal 311, and outputs the selected one asquadrature-phase component 315 of the selected transmission quadraturebaseband signal.

[0734] Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal317, i.e. signal 203 shown in FIG. 2.

[0735] An operation of modulation signal generators 202, 212 at framestructure 34 is demonstrated with reference to FIG. 36.

[0736] An operation of generator 202 is demonstrated hereinafter. Datasymbol modulation signal generator 302 receives transmission digitalsignal 301, i.e. transmission digital signal 201 of channel A in FIG.34, and frame signal 311, i.e. frame signal 210 in FIG. 34. When framesignal 311 indicates a data symbol, generator 302 outputs in-phasecomponent 303 and quadrature-phase component 304 of a transmissionquadrature baseband signal of the data symbol.

[0737] Synchronous symbol modulation signal generator 3601 receivesframe signal 311, and outputs in-phase component 3602 andquadrature-phase component 3603 of the transmission quadrature basebandsignal of the synchronous symbol when frame signal 311 indicates thesynchronous symbol.

[0738]FIG. 4 shows the signal-point placement of the respective symbolsin an in-phase-quadrature plane of the foregoing operation. Points 401in FIG. 4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 402 indicate the signal-points ofin-phase component 3602 and quadrature-phase component 3603 of thetransmission quadrature baseband signal of the synchronous symbol.

[0739] In-phase component switcher 312 receives the following signals:

[0740] in-phase component 303 of data symbol transmission quadraturebaseband signal;

[0741] in-phase component 3602 of synchronous symbol transmissionquadrature baseband signal, and frame signal 311.

[0742] Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe signal 311, and outputs the selected one as in-phase component 313of the selected transmission quadrature baseband signal.

[0743] Quadrature-phase component switcher 314 receives the followingsignals:

[0744] quadrature-phase component 304 of data symbol transmissionquadrature baseband signal;

[0745] quadrature-phase component 3603 of synchronous symboltransmission quadrature baseband signal, and frame signal 311.

[0746] Switcher 314 then selects a quadrature-phase component of atransmission quadrature baseband signal corresponding to the symbolindicated by frame signal 311, and outputs the selected one asquadrature-phase component 315 of the selected transmission quadraturebaseband signal.

[0747] Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal317, i.e. signal 203 shown in FIG. 2.

[0748] An operation of generator 202 is demonstrated hereinafter. Datasymbol modulation signal generator 302 receives transmission digitalsignal 301, i.e. transmission digital signal 201 of channel B in FIG.34, and frame signal 311, i.e. frame signal 210 in FIG. 34. When framesignal 311 indicates a data symbol, generator 302 outputs in-phasecomponent 303 and quadrature-phase component 304 of a transmissionquadrature baseband signal of the data symbol.

[0749] Guard symbol modulation signal generator 3601 receives framesignal 311. When signal 311 indicates a guard symbol, generator 3601outputs in-phase component 3602 and quadrature-phase component 3603 of atransmission quadrature baseband signal of the guard symbol.

[0750]FIG. 4 shows the signal-point placement of the respective symbolsin an in-phase-quadrature plane of the foregoing operation. Points 401in FIG. 4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 403 indicate the signal-points ofin-phase component 3602 and quadrature-phase component 3603 of thetransmission quadrature baseband signal of the guard symbol.

[0751] In-phase component switcher 312 receives the following signals:

[0752] in-phase component 303 of the data symbol transmission quadraturebaseband signal;

[0753] in-phase component 3602 of the guard symbol transmissionquadrature baseband signal, and frame signal 311.

[0754] Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe signal 311, and outputs the selected one as in-phase component 313of the selected transmission quadrature baseband signal.

[0755] Quadrature-phase component switcher 314 receives the followingsignals:

[0756] quadrature-phase components 304 of a data symbol transmissionquadrature baseband signal;

[0757] quadrature-phase component 3603 of the guard symbol transmissionquadrature baseband signal, and frame signal 311,

[0758] then selects a quadrature-phase component of a transmissionquadrature baseband signal corresponding to a symbol indicated by framesignal 311, and outputs the selected one as quadrature-phase component315 of the selected transmission quadrature baseband signal.

[0759] Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 selected as discussed above, thenprovides those components with an orthogonal modulation, and outputsmodulation signal 317, i.e. signal 213 shown in FIG. 2.

[0760] An operation of the reception apparatus is demonstratedhereinafter with reference to FIG. 37 through FIG. 42. First, theoperation is demonstrated with reference to FIG. 37.

[0761] Radio unit 3714 receives signal 3713 received by antenna 3712,then outputs reception quadrature baseband signal 3715.

[0762] Synchronizing unit 3718 receives base-band signal 3715, anddetects a synchronous symbol among the signals transmitted by thetransmission apparatus, then outputs timing signal 3719 whichsynchronizes with the transmission apparatus time-wise. Signal 3719 isused as a timing signal at the respective units in the receptionapparatus.

[0763] Next, an operation of the reception apparatus is demonstratedwith reference to FIG. 38.

[0764] Radio unit 3703 receives signal 3702 received by antenna 3701,then outputs reception quadrature baseband signal 3704.

[0765] Synchronizing unit 3801 receives base-band signal 3704, anddetects a synchronous symbol among the signals transmitted by thetransmission apparatus, then outputs timing signal 3802 whichsynchronizes with the transmission apparatus time-wise. Signal 3802 is,e.g. supplied to transmission path variation estimation unit 3705 andsignal isolator 3807. Signal 3802 then extracts a signal from base-bandsignal 3704 by timing to itself for signal processing.

[0766] Radio unit 3708 receives signal 3707 received by antenna 3706,then outputs reception quadrature baseband signal 3709.

[0767] Synchronizing unit 3803 receives base-band signal 3709, anddetects a synchronous symbol among the signals transmitted by thetransmission apparatus, then outputs timing signal 3804 whichsynchronizes with the transmission apparatus time-wise. Signal 3804 is,e.g. supplied to transmission path variation estimation unit 3710 andsignal isolator 3807. Signal 3802 then extracts a signal from base-bandsignal 3709 by timing to itself for signal processing.

[0768] Radio unit 3714 receives signal 3713 received by antenna 3712,then outputs reception quadrature baseband signal 3715.

[0769] Synchronizing unit 3805 receives base-band signal 3715, anddetects a synchronous symbol among the signals transmitted by thetransmission apparatus, then outputs timing signal 3806 whichsynchronizes with the transmission apparatus time-wise. Signal 3806 is,e.g. supplied to transmission path variation estimation unit 3716 andsignal isolator 3807. Signal 3802 then extracts a signal from base-bandsignal 3715 by timing to itself for signal processing.

[0770] Next, an operation of the reception apparatus is demonstratedwith reference to FIG. 39.

[0771] Received signal strength intensity estimation unit 3901 receivessignal 3702 received by antenna 3701, then estimates the receptionreceived signal strength intensity, and outputs received signal strengthintensity estimation signal 3902.

[0772] In a similar way to what is discussed above, received signalstrength intensity estimation unit 3903 receives signal 3707 received byantenna 3706, then estimates the reception received signal strengthintensity, and outputs received signal strength intensity estimationsignal 3904. Received signal strength intensity estimation unit 3905receives signal 3713 received by antenna 3712, then estimates thereception received signal strength intensity, and outputs receivedsignal strength intensity estimation signal 3906.

[0773] Synchronizing unit 3907 receives reception quadrature basebandsignal 3704, and detects a synchronous symbol among the signalstransmitted by the transmission apparatus, then outputs timing signal3908 which synchronizes with the transmission apparatus time-wise.

[0774] In a similar way to what is discussed above, synchronizing unit3909 receives reception quadrature baseband signal 3709, and detects asynchronous symbol among the signals transmitted by the transmissionapparatus, then outputs timing signal 3910 which synchronizes with thetransmission apparatus time-wise. Synchronizing unit 3911 receivesreception quadrature baseband signal 3715, and detects a synchronoussymbol among the signals transmitted by the transmission apparatus, thenoutputs timing signal 3912 which synchronizes with the transmissionapparatus time-wise.

[0775] Synchronous signal selection unit 3913 receives received signalstrength intensity estimation signals 3902, 3904, 3906, and timingsignals 3908, 3910, 3912. When the electric field of the signal receivedby, e.g. antenna 3701 is the strongest among others, timing signal 3908is selected from the foregoing estimation signals. Selection unit 3913then outputs timing signal 3908 selected as timing signal 3914. As such,the timing signal found from the reception signal that has the bestelectric field is used as the timing signal of the reception apparatus.

[0776] Next, an operation of the reception apparatus is demonstratedwith reference to FIG. 40.

[0777] Signal selection unit 4001 receives the following signals:

[0778] received signal strength intensity estimation signals 3902, 3904,3906; and

[0779] reception quadrature baseband signals 3704, 3709, 3715,

[0780] When the electric field of the signal received by, e.g. antenna3701 is the strongest among others, base-band signal 3704 is selectedfrom the foregoing base-band signals. Then unit 4001 outputs signal 3704as reception quadrature baseband signal 4002.

[0781] Synchronizing unit 4003 receives reception quadrature basebandsignal 4002 selected, and searches for a synchronous symbol transmittedby the transmission apparatus, then outputs timing signal 4004 whichsynchronizes with the transmission apparatus. As such, the timing signalfound from the reception signal that has the best electric field is usedas the timing signal of the reception apparatus.

[0782] Next, an operation of the reception apparatus is demonstratedwith reference to FIG. 41. The operation shown in FIG. 41 differs fromthat of FIG. 39 in finding the received signal strength intensity byusing a reception quadrature baseband signal.

[0783] Received signal strength intensity estimation unit 3901 receivesreception quadrature baseband signal 3704, then estimates the receptionreceived signal strength intensity, and outputs received signal strengthintensity estimation signal 3902.

[0784] In a similar way to what is discussed above, received signalstrength intensity estimation unit 3903 receives reception quadraturebaseband signal 3709, then estimates the reception received signalstrength intensity, and outputs received signal strength intensityestimation signal 3904. Received signal strength intensity estimationunit 3905 receives reception quadrature baseband signal 3715, thenestimates the reception received signal strength intensity, and outputsreceived signal strength intensity estimation signal 3906.

[0785] The operation shown in FIG. 42 differs from that of FIG. 40 infinding the received signal strength intensity by using a receptionquadrature baseband signal.

[0786] In the foregoing discussion, the received signal strengthintensity is used as an example of a parameter of the radio-wavepropagation environment; however, this embodiment is not limited to thisexample, and Doppler frequency or the number of paths of multi-path canbe used as the parameter.

[0787] The foregoing discussion proves that the transmission apparatuscan be synchronized with the reception apparatus time-wise.

[0788] In this embodiment, the number of channels to be multiplexed aretwo; however, other numbers can be applicable to the embodiment. Theframe structure is not limited to what is shown in FIG. 33, or FIG. 34.A modulation method of the data symbol is not limited to QPSKmodulation, but respective channels can undergo different modulations.On the other hand, all the channels can use the spread spectrumcommunication method. The spread spectrum communication method cancoexist with the other methods.

[0789] The synchronous symbols shown in FIGS. 33, 34 are used fortime-synchronizing the reception apparatus with the transmissionapparatus; however, the symbols are not limited to this usage, and theycan be used for, e.g. estimating a frequency offset between thereception apparatus and the transmission apparatus.

[0790] The structure of the transmission apparatus of this embodiment isnot limited to what is shown in FIGS. 2, 35, 36, and when the number ofchannels increases, the structure formed of elements 201 through 208shown in FIG. 31 is added accordingly.

[0791] The structure of the reception apparatus of this embodiment isnot limited to what is shown in FIG. 37 through FIG. 42; but the numberof antennas can be increased.

[0792] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0793] The eighth exemplary embodiment, as discussed above, describesthe transmission method of multiplexing modulation signals of aplurality of channels to the same frequency band, more particularly, themethod of transmitting a synchronous symbol in the foregoingtransmission method. This embodiment also describes the transmissionapparatus and the reception apparatus to be used in the foregoingtransmission method. The method and the apparatuses can increase thetransmission rate of data, and synchronize the transmission apparatuswith the reception apparatus time-wise.

[0794] Exemplary Embodiment 9

[0795] The ninth exemplary embodiment describes a transmission method oftransmitting modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas, more particularly, a methodof transmitting a synchronous symbol in the spread-spectrum transmissionmethod. The ninth embodiment also describes a transmission apparatus anda reception apparatus to be used in the foregoing transmission method.

[0796]FIG. 4 shows a placement of signal points in thein-phase-quadrature plane in accordance with this embodiment.

[0797]FIG. 12 shows a structure of the transmission apparatus inaccordance with the eighth embodiment.

[0798]FIG. 43 shows a frame structure along a time-axis in accordancewith this embodiment, and to be more specific, it shows frame structure4310 of spread-spectrum communication method A and frame structure 4320of method B. Frame structures 4310, 4320 include synchronous symbols4301, 4305, guard symbols 4302, 4304, and data symbols 4303, 4306.

[0799]FIG. 44 shows a frame structure along a time axis in accordancewith this embodiment, specifically, frame structure 4410 of method A andframe structure 4420 of method B. Structures 4410, 4420 includesynchronous symbols 3401, data symbols 3402, 3404, and guard symbol4403.

[0800]FIG. 45 shows a frame structure along a time axis in accordancewith this embodiment, specifically, frame structure 4510 of method A andframe structure 4520 of method B. Structures 4510, 4520 include guardsymbols 4503, 4505, 4507, data symbols 4502, 4504, 4506, 4508 andsynchronous symbol 4501.

[0801]FIG. 46 shows a structure of modulation signal generators 1202,1210, and the elements operating in a similar way to those in FIG. 13have the same reference marks.

[0802] Guard symbol modulation signal generator 4601 receives framesignal 1320. When signal 1320 indicates a guard symbol, generator 4601outputs in-phase component 4602 and quadrature-phase component 4603 of atransmission quadrature baseband signal of the guard symbol.

[0803] Synchronous symbol modulation signal generator 4604 receivesframe signal 1320, and outputs in-phase component 4605 andquadrature-phase component 4606 of the transmission quadrature basebandsignal of the synchronous symbol when frame signal 1320 indicates thesynchronous symbol.

[0804]FIG. 47 shows a structure of modulation signal generators 1202,1210 shown in FIG. 12, and the elements operating in a similar way tothose in FIG. 13 have the same reference marks.

[0805] Guard symbol or synchronous symbol modulation signal generator4701 receives frame signal 1320, and outputs in-phase component 4702,quadrature-phase component 4703 of a transmission quadrature basebandsignal of the guard symbol or the synchronous symbol.

[0806]FIG. 48 shows a structure of modulation signal generators 1202,1210 shown in FIG. 12, and the elements operating in a similar way tothose in FIG. 13 have the same reference marks.

[0807] Primary modulator 4802 receives control information 4801 andframe signal 1320, and outputs in-phase component 4803, quadrature-phasecomponent 4804 of the transmission quadrature baseband signal undergonethe primary modulation.

[0808] Synchronous symbol transmission signal generator 4805 receivesframe signal 1320, and outputs in-phase component 4806, quadrature-phasecomponent 4807 of the transmission quadrature baseband signal of thesynchronous symbol.

[0809] Spread unit 4808 receives the following signals:

[0810] in-phase component 4803 and quadrature-phase component 4804 ofthe transmission quadrature baseband signal undergone the primarymodulation;

[0811] in-phase component 4806, quadrature-phase component 4807 of thesynchronous symbol transmission quadrature baseband signal;

[0812] spread code 1317; and

[0813] frame signal 1320.

[0814] Spread unit 4808 then outputs in-phase component 4809 andquadrature-phase component 4810 of a transmission quadrature basebandsignal corresponding to frame signal 1320 and undergone the spread ofthe symbol.

[0815]FIG. 49 shows a structure of modulation signal generators 1202,1210 shown in FIG. 12, and the elements operating in a similar way tothose in FIG. 13 or FIG. 48 have the same reference marks.

[0816] Guard symbol modulation signal generator 4901 receives framesignal 1320, then outputs in-phase component 4902 and quadrature-phasecomponent 4903 of a transmission quadrature baseband signal of the guardsymbol.

[0817] Spread unit 4808 receives the following signals:

[0818] in-phase component 4803 and quadrature-phase component 4804 ofthe transmission quadrature baseband signal undergone the primarymodulation;

[0819] in-phase component 4902, quadrature-phase component 4903 of thesynchronous symbol transmission quadrature baseband signal;

[0820] spread code 1317; and

[0821] frame signal 1320.

[0822] Spread unit 4808 then outputs in-phase component 4809 andquadrature-phase component 4810 of a transmission quadrature basebandsignal corresponding to frame signal 1320 and undergone the spread ofthe symbol.

[0823]FIG. 37 shows a structure of a reception apparatus in accordancewith this exemplary embodiment.

[0824]FIG. 38 shows a structure of a reception apparatus in accordancewith this exemplary embodiment.

[0825]FIG. 39 shows a structure of a reception apparatus in accordancewith this exemplary embodiment.

[0826]FIG. 40 shows a structure of a reception apparatus in accordancewith this exemplary embodiment.

[0827]FIG. 41 shows a structure of a reception apparatus in accordancewith this exemplary embodiment.

[0828]FIG. 42 shows a structure of a reception apparatus in accordancewith this exemplary embodiment.

[0829] An operation of the transmission apparatus is demonstrated withreference to FIGS. 4, 12, and FIG. 43 through FIG. 49.

[0830] In FIG. 12, frame signal generator 1217 outputs the informationabout the frame structure shown in FIG. 43, FIG. 44, or FIG. 45 as framesignal 1218. Modulation signal generator 1202 of spread-spectrumcommunication method A receives frame signal 1218 and transmissiondigital signal 1201 of spread spectrum transmission method A, thenoutputs modulation signal 1203 of method A in accordance with the framestructure. Modulation signal generator 1210 of method B receives framesignal 1218 and transmission digital signal 1209 of spread spectrumtransmission method B, then outputs modulation signal 1211 of method Bin accordance with the frame structure.

[0831] Operations of modulation signal generators 1202 and 1210 in thecase of the frame structure shown in FIG. 43 are demonstrated withreference to FIG. 46. At a transmitter of spread-spectrum communicationmethod A, guard-symbol transmission signal generator 4601 shown in FIG.46 receives frame signal 1320. When signal 1320 indicates the guardsymbol, generator 4601 outputs in-phase component 4602 andquadrature-phase component 4603 of the guard symbol transmissionquadrature baseband signal.

[0832] Synchronous symbol transmission signal generator 4604 receivesframe signal 1320. When signal 1320 indicates the synchronous symbol,generator 4604 outputs in-phase component 4605, quadrature-phasecomponent 4606 of the transmission quadrature baseband signal of thesynchronous symbol.

[0833]FIG. 4 shows the signal-point placement of the respective symbolsin an in-phase-quadrature plane of the foregoing operation. Points 401in FIG. 4 indicate the signal-points of in-phase components 1311, 1318and quadrature-phase component 1312, 1319 of the transmission quadraturebaseband signal of the data symbol. Points 402 indicate thesignal-points of in-phase component 4605 and quadrature-phase component4606 of the transmission quadrature baseband signal of the synchronoussymbol. Point 403 indicates the signal-points of in-phase component 4602and quadrature-phase component 4603 of the transmission quadraturebaseband signal of the guard symbol.

[0834] Operations of modulation signal generators 1202, 1210 in the caseof the frame structure shown in FIG. 44 are demonstrated with referenceto FIG. 47 taking the transmitters of spread spectrum communicationmethods A and B as examples.

[0835]FIG. 47 shows a detailed structure of modulation signal generator1202 at the transmitter of method A. Guard symbol or synchronous symbolmodulation signal generator 4701 receives frame signal 1320, and outputsin-phase component 4702, quadrature-phase component 4703 of atransmission quadrature baseband signal of the guard symbol or thesynchronous symbol when signal 1320 indicates the synchronous symbol.

[0836]FIG. 47 shows a detailed structure of modulation signal generator1202 at the transmitter of method B. Guard symbol or synchronous symbolmodulation signal generator 4701 receives frame signal 1320, and outputsin-phase component 4702, quadrature-phase component 4703 of atransmission quadrature baseband signal of the guard symbol or thesynchronous symbol when signal 1320 indicates the guard symbol.

[0837]FIG. 4 shows the signal-point placement of the respective symbolsin an in-phase-quadrature plane of the foregoing operation. Points 401in FIG. 4 indicate the signal-points of in-phase components 1311, 1318and quadrature-phase component 1312, 1319 of the transmission quadraturebaseband signal of the data symbol. Points 402 indicate thesignal-points of the in-phase component and the quadrature-phasecomponent of the transmission quadrature baseband signal of thesynchronous symbol. Point 403 indicates the signal-points of thein-phase component and the quadrature-phase component of thetransmission quadrature baseband signal of the guard symbol.

[0838] Operations of modulation signal generators 1202, 1210 in the caseof the frame structure shown in FIG. 45 are demonstrated with referenceto FIGS. 48, 49 taking the transmitters of spread spectrum communicationmethods A and B as examples.

[0839]FIG. 48 shows a detailed structure of modulation signal generator1202 at the transmitter of method A. Primary modulator 4802 shown inFog. 48 receives control information 4801, frame signal 1320, andoutputs in-phase component 4803, quadrature-phase component 4804 of atransmission quadrature baseband signal of the control information.

[0840] Synchronous symbol transmission signal generator 4805 receivesframe signal 1320. When signal 1320 indicates the synchronous symbol,generator 4805 outputs in-phase component 4806, quadrature-phasecomponent 4807 of the transmission quadrature baseband signal of thesynchronous symbol.

[0841] Spread unit 4808 receives in-phase component 4803 andquadrature-phase component 4804 of the quadrature baseband signal of thecontrol information, in-phase component 4806, quadrature-phase component4807 of the transmission quadrature baseband signal of the synchronoussymbol, spread code 1317, frame signal 1320. Spread unit 4808 thenmultiplies code 1317 by the transmission quadrature baseband signal ofthe symbol indicated by frame signal 1320, and outputs in-phasecomponent 4809 and quadrature-phase component 4810 of a transmissionquadrature baseband signal of a control channel undergone the spread.

[0842]FIG. 49 shows a detailed structure of guard symbol modulationsignal generator 1212 at the transmitter of method B. Guard symbolmodulation signal generator 4901 receives frame signal 1320. When signal1320 indicates the guard symbol, generator 4901 outputs in-phasecomponent 4902, quadrature-phase component 4903 of a transmissionquadrature baseband signal of the guard symbol.

[0843] Spread unit 4808 receives the following signals:

[0844] in-phase component 4803 and quadrature-phase component 4804 ofthe transmission quadrature baseband signal;

[0845] in-phase component 4902, quadrature-phase component 4903 of theguard symbol transmission quadrature baseband signal;

[0846] spread code 1317; and

[0847] frame signal 1320.

[0848] Spread unit 4808 then multiplies spread code 1317 by thetransmission quadrature baseband signal of the symbol indicated by framesignal 1320, and outputs in-phase component 4809 and quadrature-phasecomponent 4810 of a transmission quadrature baseband signal of thecontrol channel.

[0849]FIG. 4 shows the signal-point placement of the respective symbolsin an in-phase-quadrature plane of the foregoing operation. Points 401in FIG. 4 indicate the signal-points of in-phase components andquadrature-phase components of the data symbol and the control symbol.Points 402 indicate the signal-points of the in-phase component and thequadrature-phase component of the transmission quadrature basebandsignal of the synchronous symbol. Point 403 indicates the signal-pointsof the in-phase component and the quadrature-phase component of thetransmission quadrature baseband signal of the guard symbol.

[0850] An operation of the reception apparatus is demonstrated withreference to FIG. 37 through FIG. 42, in those drawings, demodulators3723, 3725 carries out demodulation following the spread-spectrumcommunication method, namely, carries out inverse spread, then carriesout demodulation.

[0851] In the foregoing discussion, the received signal strengthintensity is used as an example of a parameter of the radio-wavepropagation environment; however, this embodiment is not limited to thisexample, and Doppler frequency or the number of paths of multi-path canbe used as the parameter.

[0852] The foregoing discussion proves that the transmission apparatuscan be synchronized with the reception apparatus time-wise.

[0853] In this embodiment, the number of channels to be multiplexed aretwo; however, other numbers can be applicable to the embodiment. Theframe structure is not limited to what is shown in FIG. 43, FIG. 44, orFIG. 45. Both of spread-spectrum communication methods A and B use twochannels multiplied; however, they are not limited to the two channels.

[0854] The synchronous symbols shown in FIGS. 43, 44 and 45 are used fortime-synchronizing the reception apparatus with the transmissionapparatus; however, the symbols are not limited to this usage, and theycan be used for, e.g. estimating a frequency offset between thereception apparatus and the transmission apparatus.

[0855] The structure of the transmission apparatus of this embodiment isnot limited to what is shown in FIGS. 12, 13, and when the number ofspread-spectrum communication methods increases, the structure formed ofelements 1201 through 1208 shown in FIG. 12 are added accordingly. Whenthe number of channels increases, elements 1306, 1309 increaseaccordingly.

[0856] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0857] The ninth exemplary embodiment, as discussed above, describes thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, moreparticularly, the method of transmitting the synchronous symbol in thespread-spectrum transmission method. The ninth embodiment also describesthe transmission apparatus and the reception apparatus to be used in theforegoing transmission method. The foregoing structure and operationallows increasing the data transmission rate, and synchronizing thetransmission apparatus with the reception apparatus time-wise.

[0858] Exemplary Embodiment 10

[0859] The tenth exemplary embodiment describes a transmission method oftransmitting modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas, more particularly, a methodof transmitting a synchronous symbol in accordance with OFDM method. Thetenth embodiment also describes a transmission apparatus and a receptionapparatus to be used in the foregoing method.

[0860]FIG. 4 shows a placement of signal points in thein-phase-quadrature plane in accordance with this embodiment.

[0861]FIG. 25 shows a structure of the transmission apparatus inaccordance with this embodiment.

[0862]FIG. 50 shows a frame structure along a frequency-axis inaccordance with this embodiment, and to be more specific, it shows framestructure 5010 of channel A and frame structure 5020 of channel B. Framestructures 5010, 5020 include synchronous symbol 5001, data symbols5002.

[0863]FIG. 51 shows a frame structure along a frequency-axis inaccordance with this embodiment, and to be more specific, it shows framestructure 5110 of channel A and frame structure 5120 of channel B. Framestructures 5110, 5120 include synchronous symbol 5101, data symbols5102.

[0864]FIG. 52 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 26 have the same reference marks.

[0865] Synchronizing unit 5201 receives reception quadrature basebandsignal 2604, then synchronizes with the transmission apparatustime-wise, and outputs timing signal 5204.

[0866] Synchronizing unit 5203 receives reception quadrature basebandsignal 2614, then synchronizes with the transmission apparatustime-wise, and outputs timing signal 5204.

[0867]FIG. 53 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 26 have the same reference marks.

[0868] Synchronizing unit 5301 receives reception quadrature basebandsignal 2604, then synchronizes with the transmission apparatustime-wise, and outputs timing signal 5302.

[0869]FIG. 54 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, or FIG. 39 have the same reference marks.

[0870] Discrete Fourier transformer 5401 receives reception quadraturebaseband signal 3704, timing signal 3914 selected, then outputs signal5402 undergone the discrete Fourier transformation.

[0871] In a similar way, discrete Fourier transformer 5403 receivesreception quadrature baseband signal 3709, timing signal 3914 selected,then outputs signal 5404 undergone the discrete Fourier transformation.

[0872] Discrete Fourier transformer 5405 receives reception quadraturebaseband signal 3715, timing signal 3914 selected, then outputs signal5406 undergone the discrete Fourier transformation.

[0873]FIG. 55 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, FIG. 40 or FIG. 50 have the same referencemarks.

[0874]FIG. 56 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, or FIG. 54 have the same reference marks.

[0875]FIG. 57 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, FIG. 40 or FIG. 54 have the same referencemarks.

[0876] An operation of the transmission apparatus is demonstratedhereinafter with reference to FIGS. 4, 25, 50 and 51. First, thetransmission apparatus that transmits modulation signals having theframe structure shown in FIG. 25 is described.

[0877] Frame signal generator 2521 shown in FIG. 25 outputs theinformation about the frame structure shown in FIG. 50 as frame signal2522.

[0878] In FIG. 50, a synchronous symbol is transmitted through channel Aat time 0, no signal is transmitted through channel B, in other words,the signal is indicated by signal point 403 shown in FIG. 4. In asimilar manner, when a synchronous symbol is transmitted through channelB at time 1, no signal is transmitted through channel A, in other words,the signal is indicated by signal point 403 shown in FIG. 4.

[0879] An operation of the transmission apparatus, which transmits amodulation signal having the frame structure shown in FIG. 51, isdemonstrated hereinafter. Frame signal generator 2521 shown in FIG. 25outputs the information about the frame structure shown in FIG. 51 asframe signal 2522. In FIG. 55, a synchronous symbol is transmittedthrough channel A at time 0, no signal is transmitted through channel B,in other words, the signal is indicated by signal point 403 shown inFIG. 4.

[0880] Next, an operation of the reception apparatus in accordance withthis embodiment is demonstrated with reference to FIG. 50 through FIG.57.

[0881] In FIG. 52, synchronizing unit 5201 receives reception quadraturebaseband signal 2604, then detects the synchronous symbol transmitted asshown in FIG. 50 or FIG. 51 for synchronizing with the transmissionapparatus time-wise, and outputs timing signal 5202.

[0882] Discrete Fourier transformer 2605 receives reception quadraturebaseband signal 2604, timing signal 5202, then provides base-band signal2604 with discrete Fourier transformation based on timing signal 5202,and outputs signal 2606 undergone the discrete Fourier transformation.

[0883] Synchronizing unit 5203 receives reception quadrature basebandsignal 2614, then detects the synchronous symbol transmitted as shown inFIG. 50 or FIG. 51 for synchronizing with the transmission apparatustime-wise, and outputs timing signal 5204.

[0884] Discrete Fourier transformer 2615 receives reception quadraturebaseband signal 2614, timing signal 5204, then provides base-band signal2614 with discrete Fourier transformation based on timing signal 5204,and outputs signal 2616 undergone the discrete Fourier transformation.

[0885] In FIG. 53, synchronizing unit 5301 receives reception quadraturebaseband signal 2604, then detects the synchronous symbol transmitted asshown in FIG. 50 or FIG. 51 for synchronizing with the transmissionapparatus time-wise, and outputs timing signal 5302.

[0886] Discrete Fourier transformer 2605 receives reception quadraturebaseband signal 2604, timing signal 5302, then provides base-band signal2604 with discrete Fourier transformation based on timing signal 5302,and outputs signal 2606 undergone the discrete Fourier transformation.

[0887] Discrete Fourier transformer 2615 receives reception quadraturebaseband signal 2614, timing signal 5302, then provides base-band signal2614 with discrete Fourier transformation based on timing signal 5302,and outputs signal 2616 undergone the discrete Fourier transformation.

[0888] In FIG. 54, discrete Fourier transformer 5401 receives receptionquadrature baseband signal 3704, timing signal 3914 received by theantenna having the best electric field, then provides base-band signal3704 with discrete Fourier transformation based on timing signal 3914,and outputs signal 5402 undergone the discrete Fourier transformation.

[0889] In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 3914 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 3914, and outputs signal 5404undergone the discrete Fourier transformation.

[0890] Discrete Fourier transformer 5405 receives reception quadraturebaseband signal 3715, timing signal 3914 received by the antenna havingthe best electric field, then provides base-band signal 3715 withdiscrete Fourier transformation based on timing signal 3914, and outputssignal 5406 undergone the discrete Fourier transformation.

[0891] In FIG. 55, discrete Fourier transformer 5401 receives receptionquadrature baseband signal 3704, timing signal 4004 received by theantenna having the best electric field, then provides base-band signal3704 with discrete Fourier transformation based on timing signal 4004,and outputs signal 5402 undergone the discrete Fourier transformation.

[0892] In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 4004 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 4004, and outputs signal 5404undergone the discrete Fourier transformation.

[0893] Discrete Fourier transformer 5405 receives reception quadraturebaseband signal 3715, timing signal 4004 received by the antenna havingthe best electric field, then provides base-band signal 3715 withdiscrete Fourier transformation based on timing signal 4004, and outputssignal 5406 undergone the discrete Fourier transformation.

[0894] In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 3914 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 3914, and outputs signal 5404undergone the discrete Fourier transformation.

[0895] Discrete Fourier transformer 5405 receives reception quadraturebaseband signal 3715, timing signal 3914 received by the antenna havingthe best electric field, then provides base-band signal 3715 withdiscrete Fourier transformation based on timing signal 3914, and outputssignal 5406 undergone the discrete Fourier transformation.

[0896] In FIG. 57, discrete Fourier transformer 5401 receives receptionquadrature baseband signal 3704, timing signal 4004 received by theantenna having the best electric field, then provides base-band signal3704 with discrete Fourier transformation based on timing signal 4004,and outputs signal 5402 undergone the discrete Fourier transformation.

[0897] In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 4004 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 4004, and outputs signal 5404undergone the discrete Fourier transformation.

[0898] Discrete Fourier transformer 5405 receives reception quadraturebaseband signal 3715, timing signal 4004 received by the antenna havingthe best electric field, then provides base-band signal 3715 withdiscrete Fourier transformation based on timing signal 4004, and outputssignal 5406 undergone the discrete Fourier transformation.

[0899] In the foregoing discussion, the received signal strengthintensity is used as an example of a parameter of the radio-wavepropagation environment; however, this embodiment is not limited to thisexample, and Doppler frequency or the number of paths of multi-path canbe used as the parameter.

[0900] The foregoing discussion proves that the transmission apparatuscan be synchronized with the reception apparatus time-wise.

[0901] In this embodiment, two transmission antennas are used for thedescription purpose; however, this embodiment is not limited to the twoantennas, and two channels are multiplexed for the description purpose;however, this embodiment is not limited to the two channels. Framestructures are not limited to those shown in FIG. 50 and FIG. 51.

[0902] The synchronous symbols shown in FIGS. 50, 51 are used fortime-synchronizing the reception apparatus with the transmissionapparatus; however, the symbols are not limited to this usage, and theycan be used for, e.g. estimating a frequency offset between thereception apparatus and the transmission apparatus.

[0903] The structure of the transmission apparatus of this embodiment isnot limited to the one shown in FIG. 25, and the structure of thereception apparatus of this embodiment is not limited to the ones shownin FIG. 52 through FIG. 57.

[0904] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0905] The tenth exemplary embodiment, as discussed above, describes thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, moreparticularly, the method of transmitting a synchronous symbol inaccordance with OFDM method. The tenth embodiment also describes thetransmission apparatus and the reception apparatus to be used in theforegoing method. The structure and the operation discussed above allowsincreasing the data transmission rate, and synchronizing thetransmission apparatus with the reception apparatus time-wise.

[0906] Exemplary Embodiment 11

[0907] The 11th exemplary embodiment describes a transmission method oftransmitting modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas, more particularly, areception apparatus which is applicable to a method of transmitting asignal including a control symbol.

[0908]FIGS. 33, 34, FIGS. 43-45, and FIGS. 50, 51 show a frame structurein accordance with this embodiment. FIG. 58 shows a structure of thereception apparatus in accordance with the 11th embodiment, and theelements operating in a similar way to those in FIG. 37 have the samereference marks.

[0909] Frequency offset estimation unit 5801 receives receptionquadrature baseband signal 5801, then estimates a frequency offset withrespect to a transmission apparatus, and outputs frequency offsetestimation signal 5802.

[0910] Frequency offset estimation unit 5803 receives receptionquadrature baseband signal 5802, then provides signal 5802 withfrequency control, and outputs, e.g. signal 5802 which becomes a sourcesignal of a radio unit.

[0911]FIG. 59 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37 have the same reference marks.

[0912] Frequency offset estimation unit 5901 receives receptionquadrature baseband signal 3704, then estimates a frequency offset, andoutputs frequency offset estimation signal 5902.

[0913] Frequency offset estimation unit 5903 receives receptionquadrature baseband signal 3709, then estimates a frequency offset, andoutputs frequency offset estimation signal 5904.

[0914] Frequency offset estimation unit 5905 receives receptionquadrature baseband signal 3715, then estimates a frequency offset, andoutputs frequency offset estimation signal 5906.

[0915] Calculation unit 5907 receives frequency offset signals 5902,5904, 5906, then, e.g. averages those signals, and outputs frequencyoffset estimation signal 5908 averaged.

[0916] Frequency controller 5909 receives averaged signal 5908, thenoutputs, e.g. signal 5910 to be a source signal of the radio unit.

[0917]FIG. 60 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37 or FIG. 39 have the same reference marks.

[0918] Frequency offset estimation unit 6001 receives receptionquadrature baseband signal 3704, then estimates a frequency offset, andoutputs frequency offset estimation signal 6002.

[0919] Frequency offset estimation unit 6003 receives receptionquadrature baseband signal 3709, then estimates a frequency offset, andoutputs frequency offset estimation signal 6004.

[0920] Frequency offset estimation unit 6005 receives receptionquadrature baseband signal 3715, then estimates a frequency offset, andoutputs frequency offset estimation signal 6006.

[0921] Calculation unit 6007 receives frequency offset signals 6002,6004, 6006, and received signal strength intensity estimation signals3902, 3904, 3906, then weights those signals with the received signalstrength intensity, and averages the frequency offset signals, thenoutputs frequency offset estimation signal 6008 averaged.

[0922] Frequency controller 6009 receives averaged signal 6008, thenoutputs, e.g. signal 6010 to be a source signal of the radio unit.

[0923]FIG. 61 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37 or FIG. 39 have the same reference marks.

[0924] Frequency offset estimation unit 6101 receives a receptionquadrature baseband signal selected, then estimates a frequency offset,and outputs frequency offset estimation signal 6012.

[0925] Frequency controller 6103 receives frequency offset estimationsignal 6102, then outputs, e.g. signal 6104 to be a source signal of theradio unit.

[0926]FIG. 62 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39 or FIG. 60 have the same reference marks.

[0927]FIG. 63 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, FIG. 40, or FIG. 61 have the same referencemarks.

[0928]FIG. 64 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 26 have the same reference marks.

[0929] Frequency offset estimation unit 6401 receives receptionquadrature baseband signal 2604, then estimates a frequency offset, andoutputs frequency offset estimation signal 6402.

[0930] Frequency offset estimation unit 6403 receives receptionquadrature baseband signal 2614, then estimates a frequency offset, andoutputs frequency offset estimation signal 6404.

[0931] Calculation unit 6405 receives frequency offset signals 6402,6404, then e.g. averages those signals, and outputs frequency offsetestimation signal 6406 averaged.

[0932] Frequency controller 6407 receives averaged signal 6406, thenoutputs, e.g. signal 6408 to be a source signal of the radio unit.

[0933]FIG. 65 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 26 have the same reference marks.

[0934] Frequency offset estimation unit 6501 receives receptionquadrature baseband signal 2604, then estimates a frequency offset, andoutputs frequency offset estimation signal 6502.

[0935] Frequency controller 6503 receives frequency offset estimationsignal 6502, then outputs, e.g. signal 6504 to be a source signal of theradio unit.

[0936]FIG. 66 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, or FIG. 54 have the same reference marks.

[0937] Frequency offset estimation unit 6601 receives receptionquadrature baseband signal 3704, then estimates a frequency offset, andoutputs frequency offset estimation signal 6602.

[0938] Frequency offset estimation unit 6603 receives receptionquadrature baseband signal 3709, then estimates a frequency offset, andoutputs frequency offset estimation signal 6604.

[0939] Frequency offset estimation unit 6605 receives receptionquadrature baseband signal 3715, then estimates a frequency offset, andoutputs frequency offset estimation signal 6606.

[0940] Calculation unit 6607 receives frequency offset signals 6602,6604, 6606, and received signal strength intensity estimation signals3902, 3904, 3906, then weights those signals with the received signalstrength intensity, and averages the frequency offset signals, thenoutputs frequency offset estimation signal 6608 averaged.

[0941] Frequency controller 6609 receives averaged signal 6608, thenoutputs, e.g. signal 6610 to be a source signal of the radio unit.

[0942]FIG. 67 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, FIG. 40 or FIG. 54 have the same referencemarks.

[0943] Frequency offset estimation unit 6701 receives receptionquadrature baseband signal 4002 selected, then estimates a frequencyoffset, and outputs frequency offset estimation signal 6702.

[0944] Frequency controller 6703 receives frequency offset estimationsignal 6702, then outputs, e.g. signal 6704 to be a source signal of theradio unit.

[0945]FIG. 68 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, FIG. 54 or FIG. 66 have the same referencemarks.

[0946]FIG. 69 shows a structure of the reception apparatus in accordancewith this embodiment, and the elements operating in a similar way tothose in FIG. 37, FIG. 39, FIG. 40, FIG. 54 or FIG. 67 have the samereference marks.

[0947] Next, in the transmission method of transmitting modulationsignals of a plurality of channels to the same frequency band from aplurality of antennas, a reception apparatus, which is applicable to amethod of transmitting a signal including a control symbol, is describedhereinafter.

[0948] Examples of the frame structure in accordance with thisembodiment are shown in FIGS. 33, 34, 43, 44, 45, 50 and 51. Thereception apparatus uses, e.g. a synchronous symbol, for estimating afrequency offset. In this case, the transmission apparatus has only onefrequency source, so that signals transmitted from the respectiveantennas are synchronized in frequency with each other.

[0949] An operation of the reception apparatus shown in FIG. 58 isdemonstrated hereinafter. Frequency offset estimation unit 5801 receivesreception quadrature baseband signal 3715, then estimates a frequencyoffset from the synchronous symbol, and outputs a frequency offsetestimation signal.

[0950] Demodulators 3723, 3725 removes the frequency offset fromfrequency offset estimation signal 5802 supplied.

[0951] Frequency controller 5803 receives frequency offset estimationsignal 5802, then removes the frequency offset therefrom, and outputssource signal 5804 of the radio unit.

[0952] Next, operations of the reception apparatus shown in FIG. 59different from those described in FIG. 58 are demonstrated. Calculationunit 5907 receives frequency offset estimation signals 5902, 5904, 5906,then averages those signals, and outputs frequency offset signal 5908averaged. This averaging of the signals can produce a more accurateestimation of the frequency offset.

[0953] Next, operations of the reception apparatus shown in FIG. 60different from those described in FIG. 58 are demonstrated. Calculationunit 6007 receives received signal strength intensity estimation signals3902, 3904, 3906, and frequency offset estimation signals 6002, 6004,6006, then weights those signals in response to the received signalstrength intensity, and outputs a frequency offset estimation signalaveraged. This operation allows increasing the reliability of thefrequency offset estimation signal having strong received signalstrength intensity, so that more accurate estimation of the frequencyoffset can be expected.

[0954] Next, operations of the reception apparatus shown in FIG. 61different from those described in FIG. 58 are demonstrated. Signalselection unit 4001 outputs a reception quadrature baseband signalhaving strong received signal strength intensity as signal 4002, so thatfrequency offset estimation unit 6101 produces more accurate estimationof the frequency offset.

[0955]FIGS. 62, 63 differ from FIGS. 60, 61 in finding the receivedsignal strength intensity from the reception quadrature baseband signal.

[0956] As discussed above, in the method of transmitting modulationsignals of a plurality of channels to the same frequency band from aplurality of antennas, and in the reception apparatus used in thespread-spectrum communication method, the frequency offset can beremoved.

[0957]FIG. 64 through FIG. 69 show structures of the reception apparatusused in OFDM transmission method, and the reception apparatus operatesin a similar way to what are shown in FIG. 58 through FIG. 63.

[0958] In the method of transmitting modulation signals of a pluralityof channels to the same frequency band from a plurality of antennas, andin the reception apparatus used in the OFDM transmission method, thefrequency offset can be removed according to the foregoing structure andoperation.

[0959] As a result, the frequency offset can be removed from both of thetransmission apparatus and the reception apparatus.

[0960] In this embodiment, the frame structure is not limited to what isshown in FIGS. 33, 34, 43, 44, 45, 50 or 51.

[0961] In the transmission apparatus and the reception apparatus, thesource signal supplied to the radio unit can be commonly used by therespective radio units equipped to the respective antennas, so that thefrequency offset can be commonly estimated to the plurality of antennas.

[0962] Similarly, in the transmission apparatus and the receptionapparatus, production of modulation signals in the transmissionapparatus as well as the source signal for synchronizing in thereception apparatus can be commonly used by the respective modulationsignal generators and synchronizing units equipped to the respectiveantennas. As a result, time-synchronization can be done commonly to theplurality of antennas.

[0963] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[0964] The 11th exemplary embodiment, as discussed above, describes thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, moreparticularly, the reception apparatus which is used in the method oftransmitting a signal including a control symbol. The structure andoperation discussed above allow increasing a data transmission rate, andallow the reception apparatus to remove frequency-offset.

[0965] Exemplary Embodiment 12

[0966] The 12th exemplary embodiment describes the following method andapparatus:

[0967] a communication method of transmitting a modulation signal to areceiver, who receives the modulation signal then estimates radio-wavepropagation environment of respective antennas, and transmits theestimated information of the radio-wave propagation environment, thenthe communication method selecting one of the following transmissionmethods based on the estimated information:

[0968] a method of transmitting the modulation signals of a plurality ofchannels to the same frequency band from the plurality of antennas; or

[0969] a method of transmitting the modulation signal of one channelfrom one antenna, and

[0970] a radio communication apparatus using the foregoing communicationmethod.

[0971] The 12th exemplary embodiment further describes the followingmethod and apparatus:

[0972] a communication method of transmitting a modulation signal to areceiver, who receives the modulation signal then estimates radio-wavepropagation environment of respective antennas, then the communicationmethod sending the information which requires one of the followingtransmission methods based on the estimated information of theradio-wave propagation environment:

[0973] a method of transmitting the modulation signals of a plurality ofchannels to the same frequency band from the plurality of antennas, or

[0974] a method of transmitting the modulation signal of one channelfrom one antenna;

[0975] then the communication method selecting, based on the requiringinformation, one of the foregoing two transmission methods, and

[0976] a radio communication apparatus using the foregoing communicationmethod.

[0977]FIG. 4 shows a placement of signal points in in-phase-quadrature(I-Q) plane. FIG. 70 shows a frame structure in accordance with thisembodiment along a time axis, to be more specific, frame structure 7040of a signal transmitted from a base station and frame structure 7050 ofa signal transmitted from a terminal. As shown in FIG. 70, framestructure 7040 includes frame structure 7020 of channel A and framestructure 7030 of channel B.

[0978] Frame structure 7020 includes information symbols 7001, 7003,7004, 7005, and guard symbol 7002 of the signal of channel A transmittedfrom the base station. Frame structure 7030 includes information symbols7007, 7009, guard symbols 7006, 7008, 7010 of the signal of channel Btransmitted from the base station. Frame structure 7050 includesinformation symbols 7011, 7012, 7013 of the signal transmitted from theterminal.

[0979]FIG. 71 shows information symbol structure 7110 of channel Asignal transmitted from the base station in accordance with thisembodiment. Structure 7110 includes multiplex information symbol 7101and data symbol 7102.

[0980]FIG. 72 shows information symbol structure 7210 of a signaltransmitted from the terminal in accordance with this embodiment.Structure 7210 includes received signal strength intensity informationsymbol 7201, transmission path variation information symbol 7202,multi-path information symbol 7203, disturbance information symbol 7204,and data symbol 7205.

[0981]FIG. 73 shows information symbol structure 7310 of a signaltransmitted from the terminal in accordance with this embodiment.Structure 7310 includes transmission method requiring information symbol7301, data symbol 7302.

[0982]FIG. 74 shows a structure of a transmission apparatus at the basestation in accordance with this embodiment. The apparatus includeschannel A transmitter 7410, channel B transmitter 7420, and frame signalgenerator 209.

[0983] Channel A transmitter 7410 is formed of modulation signalgenerator 202, radio unit 204, power amplifier 206, and antenna 208.

[0984] Channel B transmitter 7420 is formed of modulation signalgenerator 212, radio unit 214, power amplifier 216, and antenna 218.

[0985] The elements operating in a similar way to those in FIG. 13 havethe same reference marks.

[0986] Modulation signal generator 202 receives transmission digitalsignal 7401, multiplex information 7402, frame signal 210, and outputsmodulation signal 203 in accordance with the frame structure.

[0987] Frame signal generator 209 receives transmission methoddetermining information 7403, and outputs frame signal 210.

[0988] Modulation signal generator 212 receives transmission digitalsignal 7401 and frame signal 210, then outputs modulation signal 213.

[0989]FIG. 75 shows a structure of a reception apparatus at the basestation, and its radio unit 7503 receives signal 7502 received byantenna 7501, then outputs reception quadrature baseband signal 7504.

[0990] Demodulator 7505 receives reception quadrature baseband signal7504, then outputs reception digital signal 7506.

[0991] Signal isolator 7507 receives signal 7506, and outputs radio-wavepropagation environmental information or transmission method requiringinformation 7508 and reception data 7509.

[0992] Transmission method determining unit 7510 receives radio-wavepropagation environmental information or transmission method requiringinformation 7508, then outputs transmission method determininginformation 7511 and multiplex information 7512.

[0993]FIG. 76 shows a structure of a transmission apparatus at theterminal in accordance with this embodiment. Modulation signal generator7606 receives transmission digital signal 7601, radio-wave propagationenvironment estimation signals 7602, 7603, and frame signal 7605, thenoutputs transmission quadrature baseband signal 7607.

[0994] Frame signal generator 7604 outputs frame signal 7605.

[0995] Modulator 7608 receives transmission quadrature baseband signal7607, then outputs modulation signal 7609 from antenna 7610 as radiowave.

[0996]FIG. 77 shows a structure of a reception apparatus at the terminalin accordance with this embodiment. Radio unit 7703 receives signal 7702received by antenna 7701, then outputs reception quadrature basebandsignal 7704.

[0997] Multi-path estimation unit 7705 receives signal 7704, and outputsmulti-path estimation signal 7706.

[0998] Disturbance intensity estimation unit 7707 receives receptionquadrature baseband signal 7704, then outputs disturbance intensityestimation signal 7708.

[0999] Received signal strength intensity estimation unit 7709 ofchannel A receives reception quadrature baseband signal 7704, thenoutputs received signal strength intensity estimation signal 7710 ofchannel A.

[1000] Received signal strength intensity estimation unit 7711 ofchannel B receives reception quadrature baseband signal 7704, thenoutputs received signal strength intensity estimation signal 7712 ofchannel B.

[1001] Transmission distortion estimation unit 7713 of channel Areceives reception quadrature baseband signal 7704, then outputstransmission variation estimation signal 7714 of channel A.

[1002] Transmission distortion estimation unit 7715 of channel Breceives reception quadrature baseband signal 7704, then outputstransmission variation estimation signal 7716 of channel B.

[1003] Information generator 7717 receives the following signals:

[1004] multi-path estimation signal 7706;

[1005] disturbance intensity estimation signal 7708;

[1006] received signal strength intensity estimation signal 7710 ofchannel A;

[1007] received signal strength intensity estimation signal 7712 ofchannel B;

[1008] transmission path variation estimation signal 7714 of channel A;and

[1009] transmission path variation estimation signal 7716 of channel B,then generator 7717 outputs radio wave propagation environmentestimation signal 7718.

[1010] Signal isolator 7719 receives the following signals:

[1011] reception quadrature baseband signals 7704, 7729;

[1012] transmission path variation estimation signals 7714, 7739 ofchannel A; and

[1013] transmission path variation estimation signal 7716, 7741 ofchannel B,

[1014] then isolator 7719 outputs reception quadrature baseband signals7720, 7721 of channel A and channel B respectively.

[1015] Radio unit 7728 receives signal 7727 received by antenna 7726,then outputs reception quadrature baseband signal 7729.

[1016] Multi-path estimation unit 7730 receives reception quadraturebaseband signal 7729, and outputs multi-path estimation signal 7731.

[1017] Disturbance intensity estimation unit 7732 receives receptionquadrature baseband signal 7729, then outputs disturbance intensityestimation signal 7733.

[1018] Received signal strength intensity estimation unit 7734 ofchannel A receives reception quadrature baseband signal 7729, thenoutputs received signal strength intensity estimation signal 7735 ofchannel A.

[1019] Received signal strength intensity estimation unit 7736 ofchannel B receives reception quadrature baseband signal 7729, thenoutputs received signal strength intensity estimation signal 7737 ofchannel B.

[1020] Transmission distortion estimation unit 7738 of channel Areceives reception quadrature baseband signal 7729, then outputstransmission variation estimation signal 7739 of channel A.

[1021] Transmission distortion estimation unit 7740 of channel Breceives reception quadrature baseband signal 7729, then outputstransmission variation estimation signal 7741 of channel B.

[1022] Information generator 7742 receives the following signals:

[1023] multi-path estimation signal 7731;

[1024] disturbance intensity estimation signal 7733;

[1025] received signal strength intensity estimation signal 7735 ofchannel A;

[1026] received signal strength intensity estimation signal 7737 ofchannel B;

[1027] transmission path variation estimation signal 7739 of channel A;and

[1028] transmission path variation estimation signal 7741 of channel B,

[1029] then generator 7742 outputs radio wave propagation environmentestimation signal 7743.

[1030]FIG. 78 shows a structure of a transmission apparatus at theterminal in accordance with this embodiment, and the elements operatingin a similar way to those in FIG. 76 have the same reference marks.

[1031] Transmission method requiring information generator 7801 receivesradio-wave propagation environmental information 7602, 7603, thenoutputs transmission method requiring information 7802.

[1032]FIG. 84A shows a frame structure of a signal transmitted from thebase station in accordance with this embodiment, to be more specific,frame structure 8410 of channel A and frame structure 8420 of channel B.

[1033]FIG. 84B shows a frame structure of a signal transmitted from theterminal in accordance with this embodiment.

[1034] The base station transmits a modulation signal of OFDM method,and the frame structure includes guard symbol 8401 of the signaltransmitted from the base station, information symbol 8402 of the signaltransmitted from the base station, and information symbol 8403 of asignal transmitted from the terminal.

[1035] Next, the following communication method is demonstrated withreference to FIG. 4, and FIG. 70 through FIG. 77:

[1036] a communication method where a modulation signal is transmittedto a receiver, who receives the modulation signal, estimates radio-wavepropagation environment of respective antennas, and outputs theestimated information of the radio-wave propagation environment, thenthe communication method selects one of the following transmissionmethods based on the estimated information:

[1037] a plurality of antennas transmit the modulation signals of aplurality of channels to the same frequency band based on theinformation, or

[1038] one antenna transmits the modulation signal of one channel.

[1039] A radio communication apparatus using the foregoing communicationmethod is also described hereinafter.

[1040]FIG. 74 shows the structure of the transmission apparatus at thebase station. Frame signal generator 7403 receives transmission methoddetermining information 7403. Based on information 7403, generator 7403outputs, e.g. the information about one of the following framestructures as frame signal 210:

[1041] a transmission method where information symbol 7004 of channel Ashown in FIG. 70 and the information symbol of channel B aremultiplexed; and

[1042] a transmission method where information symbol 7005 of channel Ashown in FIG. 70 is transmitted; however, channel B has guard symbol7010, so that they are not multiplexed.

[1043] Transmission determining information 7403 corresponds to outputsignal 7511 from transmission method determining unit 7510.

[1044] Modulation signal generator 202 receives transmission digitalsignal 7401, multiplex information 7402, and frame signal 210, thenoutputs modulation signal 203 of the information symbol. At this time,the information symbol is formed of multiplex information symbol 7101and data symbol 7102, as shown in FIG. 71. Multiplex information symbol7101 is a symbol of multiplex information 7402, and data symbol 7102 istransmission digital signal 7401. Multiplex information 7402 correspondsto output signal 7512 from the reception apparatus shown in FIG. 75 atthe base station.

[1045] Modulation signal generator 212 receives transmission digitalsignal 7401, frame signal 210, and outputs modulation signal 213 of theguard symbol or the information symbol in response to frame signal 210,as shown in FIG. 70. At this time the modulation signal of the guardsymbol corresponds to signal point 403 shown in FIG. 4.

[1046]FIG. 75 shows the structure of the reception apparatus at the basestation. Signal isolator 7507 isolates the following signals in theframe structure shown in FIG. 72:

[1047] data symbol 7205;

[1048] received signal strength intensity information symbol 7201corresponding to the radio-wave propagation environmental information;

[1049] transmission path variation information symbol 7202;

[1050] multi-path information symbol 7203; and

[1051] disturbance information symbol 7204.

[1052] Signal isolator 7507 then outputs the information of data symbol7205 as reception data 7509, also outputs symbols 7201, 7202, 7203 and7204 as radio-wave propagation environmental information 7508.

[1053] Transmission method determining unit 7510 receives information7508, and based on this information 7508, selects the communicationmethod which selects one of the following transmission methods:

[1054] a method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas; or amethod of transmitting a modulation signal of one channel from oneantenna.

[1055] Determining unit 7510 then outputs the information of thetransmission methods as transmission method determining information 7511and multiplex information 7512.

[1056]FIG. 76 shows the transmission apparatus at the terminal. Theapparatus receives transmission digital signal 7601, radio-wavepropagation environment estimation signals 7602, 7603, and frame signal7605. According to the frame structure shown in FIG. 72, signal 7601 istreated as data symbol 7205, signals 7602, 7603 are treated as receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204. Then the transmission apparatusoutputs modulation signal 7606. Radio-wave propagation estimationsignals 7602, 7603 correspond to radio-wave propagation environmentestimation signals 7718, 7743 of the reception apparatus shown in FIG.77 at the terminal.

[1057]FIG. 77 shows the structure of the reception apparatus at theterminal. Information generator 7717 receives the following signals:

[1058] multi-path estimation signal 7706;

[1059] disturbance intensity estimation signal 7708;

[1060] received signal strength intensity estimation signal 7710 ofchannel A signals;

[1061] received signal strength intensity estimation signal 7712 ofchannel B signals;

[1062] transmission path variation estimation signal 7714 of channel A;and

[1063] transmission path variation estimation signal 7716 of channel B.

[1064] Generator 7717 then outputs radio-wave propagation environmentestimation signal 7718 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

[1065] In a similar way to the foregoing operation, informationgenerator 7742 receives the following signals:

[1066] multi-path estimation signal 7731;

[1067] disturbance intensity estimation signal 7733;

[1068] received signal strength intensity estimation signal 7735 ofchannel A signals;

[1069] received signal strength intensity estimation signal 7737 ofchannel B signals;

[1070] transmission path variation estimation signal 7739 of channel A;and

[1071] transmission path variation estimation signal 7741 of channel B.

[1072] Generator 7742 then outputs radio-wave propagation environmentestimation signal 7743 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

[1073] In conclusion, depending on a radio-wave propagation environment,the transmission method of transmitting modulation signals of aplurality of channels to the same frequency band from a plurality ofantennas can be switched to/from the transmission method of transmittingmodulation signals of a plurality of channels without multiplexing tothe same frequency band. This operation can improve the quality ofinformation.

[1074] In the foregoing operation, radio-wave propagation environmentestimation signals 7718, 7743 correspond to signals 7602, 7603 of thetransmission apparatus shown in FIG. 76 at the terminal.

[1075] Next, an operation at starting a communication is demonstratedhereinafter. When the communication starts, the base station transmitsmodulation signals by the transmission method of transmitting modulationsignals of a plurality of channels to the same frequency band from aplurality of antennas. At this time, if the terminal is not suitable forthe foregoing transmission method, the quality of reception data islowered.

[1076] In order to avoid this problem, when a communication to theterminal starts, the base station transmits modulation signals of aplurality of channels without multiplexing to the same frequency band assymbols 7001, 7006, and symbols 7002, 7007 shown in FIG. 70.

[1077] Frame signal generator 209 shown in FIG. 74 outputs frame signal210 in which the following frame structure is prepared: When acommunication to the terminal starts, modulations signals of a pluralityof channels are transmitted, without being multiplexed, to the samefrequency band as symbols 7001, 7006 and symbols 7002, 7007 shown inFIG. 70.

[1078] The reception apparatus shown in FIG. 77 at the terminalestimates a radio-wave propagation environment from the reception signalof symbols 7001, 7007 transmitted from the base station, then generatesradio-wave propagation environment estimation signals 7718, 7743.

[1079] The transmission apparatus shown in FIG. 76 at the terminaltransmits estimation signals 7718, 7743 with information symbols 7011,7012 shown in FIG. 70.

[1080] The reception apparatus shown in FIG. 75 at the terminal selectsone of the following transmission methods based on the radio-wavepropagation environment estimation information included in informationsymbol 7011 which is a part of the signal transmitted from transmissionapparatus shown in FIG. 76 at the terminal:

[1081] a method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas; or

[1082] a method of transmitting modulation signals of a plurality ofchannels without being multiplexed to the same frequency band.

[1083] In the case of, e.g. a fine environment for the radio-wavepropagation, the modulation signals of the plurality of channels aretransmitted from the plurality of antennas such as information symbols7004, 7009.

[1084] As discussed above, when the communication to the terminalstarts, modulation signals of a plurality of channels are transmittedwithout being multiplexed to the same frequency band, thereby improvingthe information quality.

[1085] In the foregoing discussion, a modulation signal indicating thatthe terminal requires a communication to the base station can betransmitted at the beginning. When the base station uses the OFDMtransmission method, what is discussed above can be also used.

[1086] Next, a communication method, which selects one of the followingtransmission methods, and a radio communication apparatus using thiscommunication method are described hereinafter with reference to FIGS.4, 70, 71, 73, 74, 75, 77 and 78. When a modulation signal istransmitted to a receiver, who receives the modulation signal andestimates radio-wave propagation environments of respective antennas,the communication method selects one of the following transmissionmethods based on the estimation:

[1087] a method of transmitting information that requires one of thefollowing two methods, and based on the information, this method selectsone of the transmission methods below:

[1088] a method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas; or

[1089] a method of transmitting a modulation signal of one channel fromone antenna.

[1090]FIG. 74 shows the structure of the transmission apparatus at thebase station. Frame signal generator 7403 receives transmission methoddetermining information 7403. Based on information 7403, generator 7403outputs, e.g. the information about one of the following framestructures as frame signal 210:

[1091] a frame structure of a transmission method where informationsymbol 7004 of channel A shown in FIG. 70 and the information symbol ofchannel B are multiplexed; or

[1092] a frame structure of a transmission method where informationsymbol 7005 of channel A shown in FIG. 70 is transmitted; however,channel B has guard symbol 7010, so that they are not multiplexed.

[1093] Transmission determining information 7403 corresponds to outputsignal 7511 from transmission method determining unit 7510.

[1094] Modulation signal generator 202 receives transmission digitalsignal 7401, multiplex information 7402, and frame signal 210, thenoutputs modulation signal 203 of the information symbol. At this time,the information symbol is formed of multiplex information symbol 7101and data symbol 7102, as shown in FIG. 71. Multiplex information symbol7101 is a symbol of multiplex information 7402, and data symbol 7102 istransmission digital signal 7401. Multiplex information 7402 correspondsto output signal 7512 from the reception apparatus shown in FIG. 75 atthe base station.

[1095] Modulation signal generator 212 receives transmission digitalsignal 7401, frame signal 210, and outputs modulation signal 213 of theguard symbol or the information symbol in response to frame signal 210,as shown in FIG. 70. At this time the modulation signal of the guardsymbol corresponds to signal point 403 shown in FIG. 4.

[1096]FIG. 75 shows the structure of the reception apparatus. Signalisolator 7507 isolates data symbol 7302 from transmission methodrequiring information symbol 7301 in the frame structure shown in FIG.73, then outputs the information of data symbol 7205 as reception data7509, and information symbol 7301 as transmission method requiringinformation 7509.

[1097] Transmission method determining unit 7510 receives information7508, then selects a communication method which selects one of thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, or atransmission method of transmitting a modulation signal of one channelfrom one antenna. Determining unit 7510 outputs the information aboutthe transmission method selected as transmission method determininginformation 7511 and multiplex information 7512.

[1098]FIG. 78 shows the structure of the transmission apparatus at theterminal. Transmission method requiring information generator 7801receives radio-wave propagation environment estimation signals 7602,7603. In response to those signals generator 7801 outputs acommunication method which selects one of the following two transmissionmethods as transmission requiring information 7802:

[1099] in the case of, e.g. a fine environment for the radio-wavepropagation, the transmission method of transmitting modulation signalsof a plurality of channels to the same frequency band from a pluralityof antennas.

[1100] in the case of, e.g. a bad environment for the radio-wavepropagation, the transmission method of transmitting a modulation signalof one channel from one antenna.

[1101] Modulation signal generator 7606 receives transmission digitalsignal 7601, frame signal 7605, and transmission requiring information7802, and modulates signal 7601 and information 7802 according to theframe structure shown in FIG. 73, then outputs transmission quadraturebaseband signal 7607. Radio-wave propagation environment estimationsignals 7602, 7603 correspond to radio-wave propagation environmentestimation signals 7718, 7743 of the reception apparatus shown in FIG.77 at the terminal.

[1102]FIG. 77 shows the structure of the reception apparatus at theterminal. Information generator 7717 receives the following signals:

[1103] multi-path estimation signal 7706;

[1104] disturbance intensity estimation signal 7708;

[1105] received signal strength intensity estimation signal 7710 ofchannel A signals;

[1106] received signal strength intensity estimation signal 7712 ofchannel B signals;

[1107] transmission path variation estimation signal 7714 of channel A;and

[1108] transmission path variation estimation signal 7716 of channel B,then generator 7717 outputs radio wave propagation environmentestimation signal 7718.

[1109] In a similar way to the foregoing operation, informationgenerator 7742 receives the following signals:

[1110] multi-path estimation signal 7731;

[1111] disturbance intensity estimation signal 7733;

[1112] received signal strength intensity estimation signal 7735 ofchannel A signals;

[1113] received signal strength intensity estimation signal 7737 ofchannel B signals;

[1114] transmission path variation estimation signal 7739 of channel A;and

[1115] transmission path variation estimation signal 7743 of channel B,

[1116] then generator 7742 outputs radio wave propagation environmentestimation signal 7743.

[1117] Radio wave propagation environment estimation signals 7718, 7743correspond to signals 7602, 7603 of the transmission apparatus shown inFIG. 78 at the terminal.

[1118] In conclusion, depending on a radio-wave propagation environment,the transmission method of transmitting modulation signals of aplurality of channels to the same frequency band from a plurality ofantennas can be switched to/from the transmission method of transmittingmodulation signals of a plurality of channels without multiplexing tothe same frequency band. This operation can increase the quality ofinformation.

[1119] Next, an operation at starting a communication is demonstratedhereinafter. When the communication starts, the base station transmitsmodulation signals by the transmission method of transmitting modulationsignals of a plurality of channels to the same frequency band from aplurality of antennas. At this time, if the terminal is not suitable forthe foregoing transmission method, the quality of reception data islowered.

[1120] In order to avoid this problem, when a communication to theterminal starts, the base station transmits modulation signals of aplurality of channels without multiplexing to the same frequency band assymbols 7001, 7006, and symbols 7002, 7007 shown in FIG. 70.

[1121] Frame signal generator 209 shown in FIG. 74 outputs frame signal210 in which the following frame structure is prepared: When acommunication to the terminal starts, modulation signals of a pluralityof channels are transmitted, without being multiplexed, to the samefrequency band as symbols 7001, 7006 and symbols 7002, 7007 shown inFIG. 70.

[1122] The reception apparatus shown in FIG. 77 at the terminalestimates a radio-wave propagation environment from the reception signalof symbols 7001, 7007 transmitted from the base station, then generatesradio-wave propagation environment estimation signals 7718, 7743.

[1123] Transmission method requiring information generator 7801 of thetransmission apparatus shown in FIG. 78 at the terminal receivesradio-wave propagation environment estimation signals 7718, 7743 whichestimate the environment from the reception signal of symbols 7001, 7007transmitted from the base station. Generator 7801 then selects one ofthe following two transmission methods:

[1124] a method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas; or

[1125] a method of transmitting modulation signals of a plurality ofchannels with out being multiplexed to the same frequency band.

[1126] Generator 7801 outputs transmission requiring information 7802,which is transmitted in the structure of the information symbol of thetransmission signal shown in FIG. 73 in accordance with, e.g.information symbol 7011 shown in FIG. 70.

[1127] The reception apparatus shown in FIG. 75 at the terminal selectsone of the following transmission methods based on the transmissionmethod requiring information symbol included in information symbol 7011which is a part of the signal transmitted from transmission apparatusshown in FIG. 78 at the terminal:

[1128] a method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas; or

[1129] a method of transmitting modulation signals of a plurality ofchannels without being multiplexed to the same frequency band.

[1130] As discussed above, when the communication to the terminalstarts, modulation signals of a plurality of channels are transmittedwithout being multiplexed to the same frequency band, thereby improvingthe information quality.

[1131] In the foregoing discussion, a modulation signal indicating thatthe terminal requires a communication to the base station can betransmitted at the beginning.

[1132] In this embodiment, what is discussed previously is applicable toany one of the following methods: single carrier method, spread-spectrumcommunication method, CDMA method (multiplexing method). In the case ofusing any one of those methods, the transmission apparatus needs aspread unit, and the reception apparatus needs an inverse-spread unit.

[1133] Hereinafter the case, where OFDM method among others is employed,is described. FIG. 84 shows a frame structure when the base stationtransmits signals by OFDM method. The transmission apparatus at the basestation transmits a modulation signal of channel A at time 0, and atthis time, the terminal receives the modulation signal transmitted bythe base station at time 0 as well as the modulation signal transmittedby the base station at time 1. The terminal then estimates a radio-wavepropagation environment such as multi-path, disturbance received signalstrength intensity, electric field intensities of channels A and Brespectively, and transmission path variations of channels A and Brespectively. The terminal transmits transmission requiring information,which requires one of the following information, to the base station:

[1134] the foregoing radio-wave propagation environment estimationinformation;

[1135] a method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas; or

[1136] a method of transmitting modulation signals of a plurality ofchannels without being multiplexed to the same frequency band.

[1137] The base station determines the transmission method based on theforegoing environment estimation information or the transmissionrequiring information. In the case of a fine environment for the radiowave propagation, channel A and channel B are multiplexed fortransmission such as time 3 and time 4 shown in FIG. 84. In the case ofa bad environment, a modulation signal of channel A only is transmittedsuch as time 5 in FIG. 84. In those cases, the transmission apparatusand the reception apparatus at the base station and the terminal can bestructured as shown in FIG. 74 through FIG. 78, which are described inthe frame structure shown in FIG. 70. What is discussed above is alsoapplicable to the case where a signal of the spread-spectrumcommunication method is modulated by OFDM method.

[1138] This embodiment refers to the case where two channels aremultiplexed, or switched to the case where one channel is used withoutbeing multiplexed; however, this example does not limit the embodiment.For instance, in the case where three channels can be multiplexed to thesame frequency band, the transmission apparatus at the base stationswitches the number of multiplexing between 1-3 channels.

[1139] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[1140] The 12th exemplary embodiment, as discussed above, proves thatthe following method and apparatus are achievable:

[1141] a communication method of transmitting a modulation signal to areceiver, who receives the modulation signal then estimates radio-wavepropagation environment of respective antennas, and transmits theestimated information of the radio-wave propagation environment, thenthe communication method selecting one of the following transmissionmethods based on the estimated information:

[1142] a method of transmitting the modulation signals of a plurality ofchannels to the same frequency band from the plurality of antennas; or

[1143] a method of transmitting the modulation signal of one channelfrom one antenna, and

[1144] a radio communication apparatus using the foregoing communicationmethod.

[1145] This operation and apparatus allows switching between theforegoing two transmission methods depending on the radio-wavepropagation environment. As a result, the information can be transmittedmore accurately.

[1146] Exemplary Embodiment 13

[1147] The 13th exemplary embodiment describes the following method, bywhich modulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

[1148] a communication method where a modulation signal of atransmission method, by which a control channel is transmitted, istransmitted to a receiver, who receives the modulation signal, estimatesradio-wave propagation environment of respective antennas from receptionsignals of the control channel, and transmits the estimated informationof the radio-wave propagation environment, then the communication methodselects one of the following transmission methods based on the estimatedinformation:

[1149] a method of transmitting the modulation signals of a plurality ofdata channels of the plurality of spread-spectrum communication methodsto the same frequency band from a plurality of antennas, or

[1150] a method of transmitting the modulation signal of one datachannel of one spread-spectrum communication method from one antenna.

[1151] The 13th embodiment also describes a radio communicationapparatus using the foregoing communication method.

[1152] The 13th exemplary embodiment further describes the followingmethod, by which modulation signals of a plurality of spread-spectrumcommunication methods can be transmitted:

[1153] a communication method where a modulation signal of thetransmission method, by which a control channel is transmitted, istransmitted to a receiver, who receives the modulation signal, estimatesradio-wave propagation environment of respective antennas from receptionsignals of the control channel, then the communication method sends theinformation which requires one of the following transmission methodsbased on the estimated information of the radio-wave propagationenvironment:

[1154] a method of transmitting the modulation signals of a plurality ofdata channels of the plurality of spread-spectrum communication methodsto the same frequency band from a plurality of antennas, or

[1155] a method of transmitting the modulation signal of a data channelof one spread-spectrum communication method from one antenna;

[1156] then the communication method selects, based on the requiringinformation, one of the foregoing two transmission methods, and

[1157] a radio communication apparatus using the foregoing communicationmethod is also described.

[1158]FIG. 4 shows a placement of signal points on thein-phase-quadrature (I-Q) plane.

[1159]FIG. 73 shows a structure of an information symbol at a terminalin accordance with this embodiment.

[1160]FIG. 75 shows a structure of a reception apparatus at a basestation in accordance with this embodiment.

[1161]FIG. 76 shows a structure of a transmission apparatus at theterminal in accordance with this embodiment.

[1162]FIG. 78 shows a structure of a transmission apparatus at theterminal in accordance with this embodiment.

[1163]FIG. 79 shows a frame structure along a time axis in accordancewith this embodiment, to be more specific, frame structure 7980 of asignal transmitted from the base station and frame structure 7990 of asignal transmitted from the terminal. One example of frame structure7980 includes the following frames:

[1164] frame structure 7960 of spread-spectrum communication method A,where frame structure 7960 is formed of data channel 7920 and controlchannel 7930, and

[1165] frame structure 7970 of spread-spectrum communication method B,where frame structure 7970 is formed of data channel 7940 and controlchannel 7950.

[1166] Frame structure 7920 includes information symbols 7901, 7902.Frame structure 7930 includes control symbols 7903, 7904, 7905, and 7906of method A.

[1167] Frame structure 7940 includes information symbols 7907, guardsymbol 7908. Frame structure 7950 includes control symbols 7909, 7910,7911, and 7912 of method B.

[1168] Information symbols 7913, 7914, and 7915 belong to the signaltransmitted from the terminal.

[1169]FIG. 80 shows a structure of the transmission apparatus at thebase station in accordance with this embodiment. The apparatus includestransmitters 8020 and 8030 responsible for spread-spectrum communicationmethods A and B respectively, and frame signal generator 209.

[1170] Transmitter 8020 of method A includes data-channel modulation andspread unit 8002, control-channel modulation and spread unit 8006,adding unit 8004, radio unit 204, power amplifier 206, and antenna 208.

[1171] Transmitter 8030 of method B includes data-channel modulation andspread unit 8009, control-channel modulation and spread unit 8012,adding unit 8011, radio unit 214, power amplifier 216, and antenna 218.

[1172] The elements operating in a similar way to those in FIG. 2 havethe same reference marks.

[1173] Data-channel modulation and spread unit 8002 receivestransmission digital signal 8001, frame signal 210, and outputstransmission quadrature baseband signal 8003 of the data channel ofmethod A.

[1174] Control-channel modulation and spread unit 8006 receivestransmission method determining information 8005, frame signal 210, andoutputs transmission quadrature baseband signal 8010 of the controlchannel of method A.

[1175] Adding unit 8004 receives base-band signals 8003 of data channeland 8010 of control channel, then add those signals together, therebyoutputting transmission quadrature baseband signal 203.

[1176] Data-channel modulation and spread unit 8009 receivestransmission digital signal 8008, frame signal 210, then outputstransmission quadrature baseband signal 8010 of the data channel ofmethod B.

[1177] Control-channel modulation and spread unit 8012 receivestransmission method determining information 8005, frame signal 210, thenoutputs transmission quadrature baseband signal 8013 of the controlchannel of method B.

[1178] Adding unit 8011 receives base-band signals 8010 of data channeland 8013 of control channel, then add those signals together, therebyoutputting transmission quadrature baseband signal 213.

[1179] Frame signal generator 209 receives transmission methoddetermining information 8005, then outputs frame signal 210.

[1180]FIG. 81 shows a structure of control symbol 8110, and details astructure of control symbols 7903, 7904, 7905, 7906, 7909, 7910, 7911,and 7912 shown in FIG. 79.

[1181] Control symbol 8110 includes multiplex information 8101, pilotsymbol 8102, and transmission power control information 8103.

[1182]FIG. 82 shows a structure of a reception apparatus at the terminalin accordance with this embodiment, and the elements operating in asimilar way to those in FIG. 77 have the same reference marks.

[1183] Received signal strength intensity estimation unit 8201 of methodA receives reception quadrature baseband signal 7704, and outputsreceived signal strength intensity estimation signal 8202 of method A.

[1184] Received signal strength intensity estimation unit 8203 of methodB receives reception quadrature baseband signal 7704, and outputsreceived signal strength intensity estimation signal 8204 of method B.

[1185] Transmission path variation estimation unit 8205 of method Areceives reception quadrature baseband signal 7704, and outputstransmission path variation estimation signal 8206 of method A.

[1186] Transmission path variation estimation unit 8207 of method Breceives reception quadrature baseband signal 7704, and outputstransmission path variation estimation signal 8208 of method B.

[1187] Information generator 7717 receives the following signals:

[1188] multi-path estimation signal 7706;

[1189] disturbance intensity estimation signal 7708;

[1190] received signal strength intensity estimation signal 8202 ofmethod A signals;

[1191] received signal strength intensity estimation signal 8204 ofmethod B signals;

[1192] transmission path variation estimation signal 8206 of method A;and

[1193] transmission path variation estimation signal 8208 of method B,then generator 7717 outputs radio wave propagation environmentestimation signal 7718.

[1194] Received signal strength intensity estimation unit 8209 of methodA receives reception quadrature baseband signal 7729, and outputselectric filed intensity estimation signal 8210 of method A.

[1195] Received signal strength intensity estimation unit 8211 of methodB receives reception quadrature baseband signal 7729, and outputselectric filed intensity estimation signal 8212 of method B.

[1196] Transmission path variation estimation unit 8213 of method Areceives reception quadrature baseband signal 7729, and outputstransmission path variation estimation signal 8214 of method A.

[1197] Transmission path variation estimation unit 8215 of method Breceives reception quadrature baseband signal 7729, and outputstransmission path variation estimation signal 8216 of method B.

[1198] Information generator 7742 receives the following signals:

[1199] multi-path estimation signal 7731;

[1200] disturbance intensity estimation signal 7733;

[1201] received signal strength intensity estimation signal 8210 ofmethod A signals;

[1202] received signal strength intensity estimation signal 8212 ofmethod B signals;

[1203] transmission path variation estimation signal 8214 of method A;and

[1204] transmission path variation estimation signal 8216 of method B,

[1205] then generator 7742 outputs radio wave propagation environmentestimation signal 7743.

[1206]FIG. 83 shows a frame structure in accordance with thisembodiment, to be more specific, frame structure 8301 of a signaltransmitted from the base station, and frame structure 8302 of a signaltransmitted from the terminal. An example of frame structure 8301includes frame structure 8303 of method A, where structure 8303 isformed of data channel 8305 and control channel 8306, and framestructure 8304 of method B, where structure 8304 is formed only datachannel 8307.

[1207]FIG. 85 shows a structure of a control symbol of control channel8510 when the base station transmits a signal of spread-spectrumcommunication method by OFDM method. Control channel 8510 includescontrol symbols 8501 through 8504 along a time axis.

[1208]FIG. 86 shows a structure of a control symbol of control channel8610 when the base station transmits a signal of spread-spectrumcommunication method by OFDM method. Control channel 8610 includescontrol symbols 8601 through 8604 along a frequency axis.

[1209] Next, the following method, by which modulation signals of aplurality of spread-spectrum communication methods can be transmitted,is described with reference to FIGS. 4, 72, 75, 76, 79, 80, 81, and 82:

[1210] a communication method where a modulation signal of atransmission method, which transmits a control channel, is transmittedto a receiver, who receives the modulation signal, estimates radio-wavepropagation environment of respective antennas from reception signals ofthe control channel, and transmits the estimated information of theradio-wave propagation environment, then the communication methodselects one of the following transmission methods based on the estimatedinformation:

[1211] a method of transmitting the modulation signals of a plurality ofdata channels of the plurality of spread-spectrum communication methodsto the same frequency band from a plurality of antennas, or

[1212] a method of transmitting the modulation signal of one datachannel of one spread-spectrum communication method from one antenna.

[1213] A radio communication apparatus using the foregoing communicationmethod is also described hereinafter.

[1214]FIG. 80 shows a structure the transmission apparatus at the basestation. Frame signal generator 209 receives transmission methoddetermining information 8005, and based on information 8005, outputs thefollowing frame structure information about one of the following twotransmission methods as frame signal 210:

[1215] a method, where, e.g. information symbol 7901 of method A andinformation symbol 7907 of method B shown in FIG. 79 are multiplexedtogether; or

[1216] a method, where, information symbol 7902 of method A istransmitted; however, method B has guard symbol 7908, so that they arenot multiplexed.

[1217] Transmission method determining information 8005 corresponds toreception apparatus 7511 shown in FIG. 75 at the base station.

[1218] Data-channel modulation and spread unit 8002 receivestransmission digital signal 8001, frame signal 210, then outputstransmission quadrature baseband signal 8003 of method A.

[1219] Data-channel modulation and spread unit 8009 receivestransmission digital signal 8008, frame signal 210, then in response toframe signal 210, outputs base-band signal 8010 of method B of the guardsymbol or the information symbol as shown in FIG. 79. At this time, themodulation signal of the guard symbol is indicated by signal point 403shown in FIG. 4.

[1220] Control channel modulation and spread unit 8006 receivestransmission method determining information 8005, then outputstransmission quadrature baseband signal 8007 containing the controlinformation for the control channel which includes, as shown in FIG. 81,multiplex information 8101, pilot symbol 8102, and transmission powercontrol information 8103.

[1221] In a similar way to what is discussed above, control channelmodulation and spread unit 8012 receives transmission method determininginformation 8005, then outputs transmission quadrature baseband signal8013 containing the control information for the control channel whichincludes, as shown in FIG. 81, multiplex information 8101, pilot symbol8102, and transmission power control information 8103.

[1222] Multiplex information 8101 shown in FIG. 81 works as a symbol fornotifying one of the following transmission methods to the terminal:

[1223] a method of multiplexing method A and method B together; or

[1224] a transmission method of transmitting method A only.

[1225]FIG. 75 shows a structure of the reception apparatus of the basestation. Signal isolator 7507 isolates data symbol 7205 from thefollowing elements corresponding to the radio-wave propagationenvironment information:

[1226] received signal strength intensity information symbol 7201;

[1227] transmission path variation information symbol 7202;

[1228] multi-path information symbol 7203; and

[1229] disturbance information symbol 7204.

[1230] Isolator 7507 then outputs the information of data symbol 7205 asreception data 7509. Isolator 7507 also outputs the information offoregoing symbols 7201 through 7204 as radio-wave propagationenvironment estimation information 7508.

[1231] Transmission method determining unit 7510 receives radio-wavepropagation environmental information, and based on this information,selects one of the following transmission methods:

[1232] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; or

[1233] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1234] Determining unit 7510 then outputs the information about thetransmission method as transmission method determining information 7511and multiplex information 7512.

[1235]FIG. 76 shows the structure of the transmission apparatus at theterminal. The apparatus receives transmission digital signal 7601,radio-wave propagation environment estimation signals 7602, 7603, andframe signal 7604. According to the frame structure shown in FIG. 72,signal 7601 is treated as data symbol 7205, signals 7602, 7603 aretreated as received signal strength intensity information symbol 7201,transmission path variation information symbol 7202, multi-pathinformation symbol 7203, and disturbance information symbol 7204. Thenthe transmission apparatus outputs modulation signal 7606. Radio-wavepropagation estimation signals 7602, 7603 correspond to radio-wavepropagation environment estimation signals 7718, 7743 of the receptionapparatus shown in FIG. 82 at the terminal.

[1236]FIG. 82 shows a structure of the reception apparatus at theterminal. Received signal strength intensity estimation unit 8201 ofmethod A receives reception quadrature baseband signal 7704, andestimates a received signal strength intensity from, e.g. a component ofthe control channel shown in FIG. 79 of method A of reception quadraturebaseband signal 7704. Estimation unit 8201 then outputs received signalstrength intensity estimation signal 8202 of method A.

[1237] Received signal strength intensity estimation unit 8203 of methodB receives reception quadrature baseband signal 7704, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method B of reception quadrature basebandsignal 7704. Estimation unit 8203 then outputs received signal strengthintensity estimation signal 8204 of method B.

[1238] Transmission path variation estimation unit 8205 of method Areceives reception quadrature baseband signal 7704, and estimates atransmission path variation from, e.g. a component of the controlchannel shown in FIG. 79 of method A, then outputs transmission pathvariation estimation signal 8206 of method A.

[1239] Transmission path variation estimation unit 8207 of method Breceives reception quadrature baseband signal 7704, and estimates atransmission path variation from, e.g. a component of the controlchannel shown in FIG. 79 of method B, then outputs transmission pathvariation estimation signal 8208 of method B.

[1240] Information generator 7717 receives the following signals:

[1241] multi-path estimation signal 7706;

[1242] disturbance intensity estimation signal 7708;

[1243] received signal strength intensity estimation signal 8202 ofmethod A signals;

[1244] received signal strength intensity estimation signal 8204 ofmethod B signals;

[1245] transmission path variation estimation signal 8206 of method A;and

[1246] transmission path variation estimation signal 8208 of method B,

[1247] then generator 7717 outputs radio wave propagation environmentestimation signal 7718 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

[1248] Received signal strength intensity estimation unit 8209 of methodA receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method A of reception quadrature basebandsignal 7729. Estimation unit 8209 then outputs received signal strengthintensity estimation signal 8210 of method A.

[1249] Received signal strength intensity estimation unit 8211 of methodB receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method B of reception quadrature basebandsignal 7729. Estimation unit 8211 then outputs received signal strengthintensity estimation signal 8212 of method B.

[1250] Received signal strength intensity estimation unit 8213 of methodA receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method A of reception quadrature basebandsignal 7729. Estimation unit 8213 then outputs received signal strengthintensity estimation signal 8214 of method A.

[1251] Received signal strength intensity estimation unit 8215 of methodB receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method B of reception quadrature basebandsignal 7729. Estimation unit 8215 then outputs received signal strengthintensity estimation signal 8216 of method B.

[1252] Information generator 7742 receives the following signals:

[1253] multi-path estimation signal 7731;

[1254] disturbance intensity estimation signal 7733;

[1255] received signal strength intensity estimation signal 8210 ofmethod A signals;

[1256] received signal strength intensity estimation signal 8212 ofmethod B signals;

[1257] transmission path variation estimation signal 8214 of method A;and

[1258] transmission path variation estimation signal 8216 of method B,then generator 7742 outputs radio wave propagation environmentestimation signal 7743 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

[1259] The foregoing discussion proves that a switch between thefollowing two transmission methods improves the information quality:

[1260] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; and

[1261] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1262] Radio-wave propagation environment estimation signals 7718, 7743correspond to signals 7602, 7603 of the transmission apparatus shown inFIG. 76 at the terminal.

[1263] Next, an operation at the start of a communication is describedhereinafter. At the start of the communication, if the base stationtransmits modulation signals of data channels of a plurality ofspread-spectrum communication methods to the same frequency band from aplurality of antennas, the terminal does not suit to this transmissionmethod because of, e.g. a bad radio-wave propagation environment. Inthis case, the quality of reception data is lowered.

[1264] The transmission signal from the base station is then preparedsuch that neither information symbols of method A nor informationsymbols of method B shown in FIG. 79 are exist. For instance, no pluraldata channels are exist at the same frequency band, such as the time ofcontrol symbol 7903 of method A and control symbol 7909 of method B, andthe time of control symbol 7904 of method A and control symbol 7913 ofmethod B as shown in FIG. 79.

[1265] Frame signal generator 209 shown in FIG. 80 prepares a framestructure at the start of a communication with the terminal such that noplural data channels are exist at the same frequency band, such as thetime of control symbol 7903 of method A and control symbol 7909 ofmethod B, and the time of control symbol 7904 of method A and controlsymbol 7913 of method B as shown in FIG. 79. Generator 209 then outputsthis frame structure as frame signal 210.

[1266] The reception apparatus shown in FIG. 82 at the terminalestimates a radio-wave propagation environment from the followingsignals, then outputs radio-wave propagation estimation signals 7718,7743:

[1267] control symbol 7903 of method A and control symbol 7909 of methodB of the transmission signal from the base station shown in FIG. 80; and

[1268] control symbol 7904 of method A and control symbol 7913 of methodB of the transmission signal from the base station shown in FIG. 80.

[1269] Transmission apparatus shown in FIG. 76 at the terminal estimatesa radio-wave propagation environment from the following signals, thenoutputs radio-wave propagation estimation signals 7718, 7743 withinformation symbols 7913, 7914 shown in FIG. 79:

[1270] control symbol 7903 of method A and control symbol 7909 of methodB of the transmission signal from the base station; and

[1271] control symbol 7904 of method A and control symbol 7913 of methodB of the transmission signal from the base station.

[1272] The reception apparatus shown in FIG. 75 at the base stationdetermines one of the following transmission methods based on theradio-wave propagation environment estimation information included ininformation symbol 7913, an element of the transmission signal from thetransmission apparatus shown in FIG. 76 at the terminal:

[1273] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; or

[1274] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1275] Then in the case of a fine environment for radio-wavepropagation, modulation signals of data channels of a plurality ofspread-spectrum communication methods are transmitted to the samefrequency band from a plurality of antennas such as information symbols7901, 7907.

[1276] The foregoing discussion proves that the preparation of no datachannels of plural spread-spectrum communication methods existing at thesame frequency band at the start of a communication with the terminalcan improve the quality of information.

[1277] In the foregoing description, a modulation signal indicating thatthe terminal requires a communication with the base station can betransmitted at the beginning.

[1278] Next, the following method, by which modulation signals of aplurality of spread-spectrum communication methods can be transmitted,is described with reference to FIGS. 4, 73, 75, 78, 79, 80, 81, and 82:

[1279] a communication method where a modulation signal of thetransmission method, which transmits a control channel, is transmittedto a receiver, who receives the modulation signal then estimatesradio-wave propagation environment of respective antennas from receptionsignals of the control channel, then the communication method sends theinformation which requires one of the following transmission methodsbased on the estimated information of the radio-wave propagationenvironment:

[1280] a method of transmitting the modulation signals of a plurality ofdata channels of the plurality of spread-spectrum communication methodsto the same frequency band from a plurality of antennas, or

[1281] a method of transmitting the modulation signal of a data channelof one spread-spectrum communication method from one antenna;

[1282] then the communication method selects, based on the requiringinformation, one of the foregoing two transmission methods, and

[1283] a radio communication apparatus using the foregoing communicationmethod is also described.

[1284]FIG. 80 shows the structure of the transmission apparatus at thebase station. Frame signal generator 209 receives transmission methoddetermining information 8005, and based on information 8005, outputs thefollowing frame structure information about one of the following twotransmission methods as frame signal 210:

[1285] a transmission method, where, e.g. information symbol 7901 ofmethod A and information symbol 7907 of method B shown in FIG. 79 aremultiplexed together; or

[1286] a transmission method, where, information symbol 7902 of method Ais transmitted; however, method B has guard symbol 7908, so that theyare not multiplexed.

[1287] Transmission method determining information 8005 corresponds toreception apparatus 7511 shown in FIG. 75 at the base station.

[1288] Data-channel modulation and spread unit 8002 receivestransmission digital signal 8001, frame signal 210, then outputstransmission quadrature baseband signal 8003 of method A.

[1289] Data-channel modulation and spread unit 8009 receivestransmission digital signal 8008, frame signal 210, then in response toframe signal 210, outputs base-band signal 8010 of method B of the guardsymbol or the information symbol as shown in FIG. 79. At this time, themodulation signal of the guard symbol corresponds to signal point 403shown in FIG. 4.

[1290] Control channel modulation and spread unit 8006 receivestransmission method determining information 8005, then outputstransmission quadrature baseband signal 8007 containing the controlinformation for the control channel which includes, as shown in FIG. 81,multiplex information 8101, pilot symbol 8102, and transmission powercontrol information 8103.

[1291] In a similar way to what is discussed above, control channelmodulation and spread unit 8012 receives transmission method determininginformation 8005, then outputs transmission quadrature baseband signal8013 containing the control information for the control channel whichincludes, as shown in FIG. 81, multiplex information 8101, pilot symbol8102, and transmission power control information 8103.

[1292] Multiplex information 8101 shown in FIG. 81 works as a symbol fornotifying one of the following transmission methods to the terminal:

[1293] a method of multiplexing method A and method B together; or

[1294] a method of transmitting method A only.

[1295]FIG. 75 shows a structure of the reception apparatus of the basestation. Signal isolator 7507 isolates data symbol 7302 fromtransmission method requiring information symbol 7301, then isolator7507 outputs the information of data symbol 7302 as reception data 7509,and outputs also the information of transmission method requiring symbol7301 as transmission requiring information 7508.

[1296] Transmission method determining unit 7510 receives transmissionrequiring information 7508, and based on this information, selects oneof the following transmission methods:

[1297] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; or

[1298] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1299] Determining unit 7510 then outputs the information about thetransmission method as transmission method determining information 7511and multiplex information 7512.

[1300]FIG. 78 shows the structure of the transmission apparatus at theterminal. Transmission method requiring information generator 7801receives radio-wave propagation environment estimation signals 7602,7603, then outputs transmission method requiring information 7802.Modulation signal generator 7606 receives transmission digital signal7601, transmission requiring information 7802, and frame signal 7605,and outputs modulation signal 7607 according to the frame structureshown in FIG. 73. Radio-wave propagation environment estimation signals7602, 7603 correspond to estimation signals 7718, 7743 of the receptionapparatus shown in FIG. 82 at the terminal.

[1301]FIG. 82 shows the structure of the reception apparatus at theterminal. Received signal strength intensity estimation unit 8201 ofspread-spectrum communication method A receives reception quadraturebaseband signal 7704, and estimates a received signal strength intensityfrom, e.g. a component of the control channel shown in FIG. 79 of methodA of reception quadrature baseband signal 7704. Estimation unit 8201then outputs received signal strength intensity estimation signal 8202of method A.

[1302] Received signal strength intensity estimation unit 8203 ofspread-spectrum communication method B receives reception quadraturebaseband signal 7704, and estimates a received signal strength intensityfrom, e.g. a component of the control channel shown in FIG. 79 of methodB of reception quadrature baseband signal 7704. Estimation unit 8203then outputs received signal strength intensity estimation signal 8204of method B.

[1303] Transmission path variation estimation unit 8205 of method Areceives reception quadrature baseband signal 7704, and estimates atransmission path variation from, e.g. a component of the controlchannel of method A shown in FIG. 79, then outputs transmission pathvariation estimation signal 8206 of method A.

[1304] Transmission path variation estimation unit 8207 of method Breceives reception quadrature baseband signal 7704, and estimates atransmission path variation from, e.g. a component of the controlchannel of method B shown in FIG. 79, then outputs transmission pathvariation estimation signal 8208 of method B.

[1305] Information generator 7717 receives the following signals:

[1306] multi-path estimation signal 7706;

[1307] disturbance intensity estimation signal 7708;

[1308] received signal strength intensity estimation signal 8202 ofmethod A signals;

[1309] received signal strength intensity estimation signal 8204 ofmethod B signals;

[1310] transmission path variation estimation signal 8206 of method A;and

[1311] transmission path variation estimation signal 8208 of method B,

[1312] then generator 7717 outputs radio wave propagation environmentestimation signal 7718 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

[1313] Received signal strength intensity estimation unit 8209 of methodA receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method A of reception quadrature basebandsignal 7729. Estimation unit 8209 then outputs received signal strengthintensity estimation signal 8210 of method A.

[1314] Received signal strength intensity estimation unit 8211 of methodB receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method B of reception quadrature basebandsignal 7729. Estimation unit 8211 then outputs received signal strengthintensity estimation signal 8212 of method B.

[1315] Received signal strength intensity estimation unit 8213 of methodA receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method A of reception quadrature basebandsignal 7729. Estimation unit 8213 then outputs received signal strengthintensity estimation signal 8214 of method A.

[1316] Received signal strength intensity estimation unit 8215 of methodB receives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g. a component of the controlchannel shown in FIG. 79 of method B of reception quadrature basebandsignal 7729. Estimation unit 8215 then outputs received signal strengthintensity estimation signal 8216 of method B.

[1317] Information generator 7742 receives the following signals:

[1318] multi-path estimation signal 7731;

[1319] disturbance intensity estimation signal 7733;

[1320] received signal strength intensity estimation signal 8210 ofmethod A signals;

[1321] received signal strength intensity estimation signal 8212 ofmethod B signals;

[1322] transmission path variation estimation signal 8214 of method A;and

[1323] transmission path variation estimation signal 8216 of method B,

[1324] then generator 7742 outputs radio wave propagation environmentestimation signal 7743 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

[1325] The foregoing discussion proves that a switch between thefollowing two transmission methods improves the information quality:

[1326] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; and

[1327] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1328] Radio-wave propagation environment estimation signals 7718, 7743correspond to signals 7602, 7603 of the transmission apparatus shown inFIG. 76 at the terminal.

[1329] Next, an operation at the start of a communication is describedhereinafter. At the start of the communication, if the base stationtransmits modulation signals of data channels of a plurality ofspread-spectrum communication methods to the same frequency band from aplurality of antennas, the terminal does not suit to this transmissionmethod because of, e.g. a bad radio-wave propagation environment. Inthis case, the quality of reception data is lowered.

[1330] The transmission signal from the base station is then preparedsuch that neither information symbols of method A nor informationsymbols of method B shown in FIG. 79 are exist. For instance, no pluraldata channels are exist at the same frequency band, such as the time ofcontrol symbol 7903 of method A and control symbol 7909 of method B, andthe time of control symbol 7904 of method A and control symbol 7913 ofmethod B as shown in FIG. 79.

[1331] Frame signal generator 209 shown in FIG. 80 prepares a framestructure at the start of a communication with the terminal such that noplural data channels are exist at the same frequency band, such as thetime of control symbol 7903 of method A and control symbol 7909 ofmethod B, and the time of control symbol 7904 of method A and controlsymbol 7913 of method B as shown in FIG. 79. Generator 209 then outputsthis frame structure as frame signal 210.

[1332] The reception apparatus shown in FIG. 82 at the terminalestimates a radio-wave propagation environment from the followingsignals, then outputs radio-wave propagation estimation signals 7718,7743:

[1333] control symbol 7903 of method A and control symbol 7909 of methodB of the transmission signal from the base station shown in FIG. 80; and

[1334] control symbol 7904 of method A and control symbol 7913 of methodB of the transmission signal from the base station shown in FIG. 80.

[1335] Transmission method requiring information generator 7801 of thetransmission apparatus shown in FIG. 78, based on radio-wave propagationenvironment estimation signals 7718 and 7743 discussed above, transmitsinformation which requires one of the following transmission method asthe transmission requiring information with information symbols 7913,7914 shown in FIG. 79:

[1336] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; or

[1337] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1338] The reception apparatus shown in FIG. 75 at the base stationdetermines one of the following transmission methods based on theradio-wave propagation environment estimation information included ininformation symbol 7913, which is an element of the transmission signalfrom the transmission apparatus shown in FIG. 76 at the terminal:

[1339] a method of transmitting modulation signals of data channels of aplurality of spread-spectrum communication methods to the same frequencyband from a plurality of antennas; or

[1340] a method of transmitting a modulation signal of a data channel ofone spread-spectrum communication method to the same frequency band fromone antenna.

[1341] Then the modulation signals of the transmission method determinedare transmitted from the antenna.

[1342] The foregoing discussion proves that the preparation of no datachannels of plural spread-spectrum communication methods existing at thesame frequency band at the start of a communication with the terminalcan improve the quality of information.

[1343] In the foregoing description, a modulation signal indicating thatthe terminal requires a communication with the base station can betransmitted at the beginning.

[1344] In the foregoing description, as shown in FIG. 79, the controlchannel exists in both of spread-spectrum communication methods A and B;however, e.g. this embodiment is applicable to the case where thecontrol channel exits only in method A, as shown in FIG. 83. In thiscase, the transmission apparatus in FIG. 80 does not have controlchannel modulation and spread unit 8012 of method B.

[1345] This embodiment refers to the case where the number ofspread-spectrum communication methods to be multiplexed are switchedbetween two channels and one channel; however, this example does notlimit the embodiment. For instance, in the case where three methods canbe multiplexed to the same frequency band, the transmission apparatus atthe base station switches the number of multiplexing between 1-3methods.

[1346] This embodiment is also applicable to the case where signals of aspread-spectrum communication method is modulated by OFDM method. Astructure of a control symbol of a spread-spectrum communication methodtransmitted from the base station in this case is shown in FIGS. 85 and86. In FIG. 85, the control symbols are spread on the time axis, whilethey are spread on the frequency axis in FIG. 86. Information symbolsare also spread either on a time axis or a frequency axis as shown inFIGS. 85 and 86, so that they are multiplexed to signals of the controlchannels. The transmission apparatus and the reception apparatus both atthe base station and the terminal can be formed of elements described inFIGS. 75, 76, 78, 80 and 82 which are referred to the frame structureshown in FIG. 70.

[1347] In this embodiment, one data channel per method A or method B isused for the description purpose; however, the number of data channelsis not limited to one, and plural data channels are applicable to thisembodiment. Codes to be used for spread or inverse-spread ofspread-spectrum communication methods A and B can be identical to eachother or different from each other.

[1348] The expression of “antenna” in the previous description does notalways mean a single antenna, but “antenna” can mean an antenna unitwhich is formed of a plurality of antennas.

[1349] The previous discussion refers to the following method, by whichmodulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

[1350] the communication method where a modulation signal of atransmission method, which transmits a control channel, is transmittedto a receiver, who receives the modulation signal then estimatesradio-wave propagation environment of respective antennas from receptionsignals of the control channel, and transmits the estimated informationof the radio-wave propagation environment, then the communication methodselects one of the following transmission methods based on the estimatedinformation:

[1351] a method of transmitting the modulation signals of a plurality ofdata channels of the plurality of spread-spectrum communication methodsto the same frequency band from a plurality of antennas, or

[1352] a method of transmitting the modulation signal of one datachannel of one spread-spectrum communication method from one antenna.

[1353] The previous discussion also refers to the radio communicationapparatus using the foregoing communication method.

[1354] The discussion above also describes the method below, by whichmodulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

[1355] the communication method where a modulation signal of thetransmission method, which transmits a control channel, is transmittedto a receiver, who receives the modulation signal then estimatesradio-wave propagation environment of respective antennas from receptionsignals of the control channel, then the communication method sends theinformation which requires one of the transmission methods below basedon the information of the estimated radio-wave propagation environment:

[1356] a method of transmitting the modulation signals of a plurality ofdata channels of the plurality of spread-spectrum communication methodsto the same frequency band from a plurality of antennas, or

[1357] a method of transmitting the modulation signal of a data channelof one spread-spectrum communication method from one antenna;

[1358] then the communication method selects, based on the requiringinformation, one of the foregoing two transmission methods. Thediscussion above also refers to the radio communication apparatus usingthe communication method. In conclusion, the methods and the apparatusesdiscussed above allow transmitting information more accurately.

INDUSTRIAL APPLICABILITY

[1359] The present invention is useful for a transmission and receptionmethod by which modulation signals of a plurality of channels aremultiplexed to the same frequency band. The present invention allowsestimating channels accurately and with ease for demultiplexingmultiplexed modulation signals received by a reception apparatus.

1. A reception apparatus comprising: a plurality of antennas forreceiving modulation signals of a plurality of channels available in anidentical frequency band; a field electric intensity estimation unit forestimating a reception field electric intensity of reception signalsreceived by the plurality of antennas, and outputting a receptionreceived signal strength intensity estimation signal of respectivereception signals; a transmission path fluctuation estimation unit forestimating a transmission path fluctuation of respective channels of therespective reception signals, and outputting a transmission pathfluctuation estimation signal; a phase difference estimation unit forreceiving the transmission path fluctuation estimation signals of givenchannels supplied from the respective antennas, and finding a phasedifference between the transmission path fluctuation estimation signalsof the given channels, then outputting a phase difference signal; and asignal selector for receiving a reception quadrate baseband signalsupplied from the respective antennas, the transmission path fluctuationestimation signals of given channels supplied from the respectiveantennas, reception received signal strength intensity estimationsignals of the respective reception signals, and the phase differencesignal, then selecting the reception quadrate baseband signal and thetransmission path fluctuation estimation signals of given channels forisolating signals of the respective channels from the reception signalsbefore outputting the signals selected.
 2. A reception apparatuscomprising: a plurality of antennas for receiving modulation signals ofa plurality of spread-spectrum communication methods transmitted to anidentical frequency band; a field electric intensity estimation unit forestimating a reception field electric intensity of reception signalsreceived by the plurality of antennas, and outputting a receptionreceived signal strength intensity estimation signal of the respectivereception signals; a transmission path fluctuation estimation unit forestimating a transmission path fluctuation of respective spread-spectrumcommunication methods of the respective reception signals, andoutputting a transmission path fluctuation estimation signal; a phasedifference estimation unit for receiving the transmission pathfluctuation estimation signals, and finding a phase difference betweenthe transmission path fluctuation estimation signals of the givenchannels, then outputting a phase difference signal; and a signalselector for receiving a reception quadrate baseband signal suppliedfrom the respective antennas, the transmission path fluctuationestimation signals, reception received signal strength intensityestimation signals of the respective reception signals, and the phasedifference signal, then selecting the reception quadrate baseband signaland the transmission path fluctuation estimation signals for isolatingsignals of the respective spread-spectrum communication methods from thereception signals before outputting the signals selected.
 3. A receptionapparatus comprising: a plurality of antennas for receiving modulationsignals transmitted by a transmission method by which, a transmissionapparatus transmits modulation signals of a plurality of channelsavailable in an identical frequency band from a plurality of antennas,and a symbol for time-synchronization is included in a signaltransmitted from only a given antenna, and while this symbol istransmitted, in signals transmitted from other antennas, both of anidentical phase signal and an quadrate signal in the in-phase-quadratureplane are made to be zero signals, a synchronizing unit, prepared foreach one of the antennas, for synchronizing with the transmissionapparatus time-wise using a reception signal; and a radio-wavepropagation environment estimation unit, prepared for each one of theantennas, for estimating a radio-wave propagation environment from thereception signal, wherein a signal supplied from a synchronizing unitcorresponding to one of the antennas, which is estimated having the bestradio-wave propagation environment, is used as a time-synchronizationsignal for synchronizing with the transmission apparatus.
 4. A receptionapparatus comprising: a plurality of antennas for receiving modulationsignals transmitted by a transmission method by which, a transmissionapparatus transmits modulation signals of a plurality of channelsavailable in an identical frequency band from a plurality of antennas,and a symbol for estimating a frequency offset is included in a signaltransmitted from only a given antenna, and while this symbol istransmitted, in signals transmitted from other antennas, both of anidentical phase signal and an quadrate signal in an in-phase-quadratureplane are made to be zero signals; a frequency-offset estimation unit,prepared for each one of the antennas at the reception apparatus, forestimating a frequency offset between the reception apparatus and thetransmission apparatus with a reception signal; and a radio-wavepropagation environment estimation unit, prepared for each one of theantennas, for estimating a radio-wave propagation environment, wherein asignal supplied from a frequency offset estimation unit corresponding toone of the antennas, which is estimated having the best radio-wavepropagation environment, is used for removing the frequency offset.